/*
 * hunt-time: A time library for D programming language.
 *
 * Copyright (C) 2015-2018 HuntLabs
 *
 * Website: https://www.huntlabs.net/
 *
 * Licensed under the Apache-2.0 License.
 *
 */

module hunt.time.util.Calendar;

import hunt.Exceptions;
// import hunt.stream.Common;
// import java.security.AccessControlContext;
// import java.security.AccessController;
// import java.security.PermissionCollection;
// import java.security.PrivilegedActionException;
// import java.security.PrivilegedExceptionAction;
// import java.security.ProtectionDomain;
// import java.text.DateFormat;
// import java.text.DateFormatSymbols;
import hunt.time.Instant;
import hunt.collection;
import hunt.time.util.Common;
import hunt.util.Locale;
// import java.util.concurrent.ConcurrentHashMap;
// import java.util.concurrent.ConcurrentMap;
// import sun.util.BuddhistCalendar;
// import sun.util.calendar.ZoneInfo;
// import sun.util.locale.provider.CalendarDataUtility;
// import sun.util.locale.provider.LocaleProviderAdapter;
// import sun.util.locale.provider.TimeZoneNameUtility;
// import sun.util.spi.CalendarProvider;

import std.datetime;

/**
 * The <code>Calendar</code> class is an abstract class that provides methods
 * for converting between a specific instant in time and a set of {@link
 * #fields calendar fields} such as <code>YEAR</code>, <code>MONTH</code>,
 * <code>DAY_OF_MONTH</code>, <code>HOUR</code>, and so on, and for
 * manipulating the calendar fields, such as getting the date of the next
 * week. An instant in time can be represented by a millisecond value that is
 * an offset from the <a id="Epoch"><em>Epoch</em></a>, January 1, 1970
 * 00:00:00.000 GMT (Gregorian).
 *
 * <p>The class also provides additional fields and methods for
 * implementing a concrete calendar system outside the package. Those
 * fields and methods are defined as <code>protected</code>.
 *
 * <p>
 * Like other locale-sensitive classes, <code>Calendar</code> provides a
 * class method, <code>getInstance</code>, for getting a generally useful
 * object of this type. <code>Calendar</code>'s <code>getInstance</code> method
 * returns a <code>Calendar</code> object whose
 * calendar fields have been initialized with the current date and time:
 * <blockquote>
 * <pre>
 *     Calendar rightNow = Calendar.getInstance();
 * </pre>
 * </blockquote>
 *
 * <p>A <code>Calendar</code> object can produce all the calendar field values
 * needed to implement the date-time formatting for a particular language and
 * calendar style (for example, Japanese-Gregorian, Japanese-Traditional).
 * <code>Calendar</code> defines the range of values returned by
 * certain calendar fields, as well as their meaning.  For example,
 * the first month of the calendar system has value <code>MONTH ==
 * JANUARY</code> for all calendars.  Other values are defined by the
 * concrete subclass, such as <code>ERA</code>.  See individual field
 * documentation and subclass documentation for details.
 *
 * <h3>Getting and Setting Calendar Field Values</h3>
 *
 * <p>The calendar field values can be set by calling the <code>set</code>
 * methods. Any field values set in a <code>Calendar</code> will not be
 * interpreted until it needs to calculate its time value (milliseconds from
 * the Epoch) or values of the calendar fields. Calling the
 * <code>get</code>, <code>getTimeInMillis</code>, <code>getTime</code>,
 * <code>add</code> and <code>roll</code> involves such calculation.
 *
 * <h4>Leniency</h4>
 *
 * <p><code>Calendar</code> has two modes for interpreting the calendar
 * fields, <em>lenient</em> and <em>non-lenient</em>.  When a
 * <code>Calendar</code> is in lenient mode, it accepts a wider range of
 * calendar field values than it produces.  When a <code>Calendar</code>
 * recomputes calendar field values for return by <code>get()</code>, all of
 * the calendar fields are normalized. For example, a lenient
 * <code>GregorianCalendar</code> interprets <code>MONTH == JANUARY</code>,
 * <code>DAY_OF_MONTH == 32</code> as February 1.

 * <p>When a <code>Calendar</code> is in non-lenient mode, it throws an
 * exception if there is any inconsistency in its calendar fields. For
 * example, a <code>GregorianCalendar</code> always produces
 * <code>DAY_OF_MONTH</code> values between 1 and the length of the month. A
 * non-lenient <code>GregorianCalendar</code> throws an exception upon
 * calculating its time or calendar field values if any out-of-range field
 * value has been set.
 *
 * <h4><a id="first_week">First Week</a></h4>
 *
 * <code>Calendar</code> defines a locale-specific seven day week using two
 * parameters: the first day of the week and the minimal days in first week
 * (from 1 to 7).  These numbers are taken from the locale resource data or the
 * locale itself when a {@code Calendar} is constructed. If the designated
 * locale contains "fw" and/or "rg" <a href="./Locale.html#def_locale_extension">
 * Unicode extensions</a>, the first day of the week will be obtained according to
 * those extensions. If both "fw" and "rg" are specified, the value from the "fw"
 * extension supersedes the implicit one from the "rg" extension.
 * They may also be specified explicitly through the methods for setting their
 * values.
 *
 * <p>When setting or getting the <code>WEEK_OF_MONTH</code> or
 * <code>WEEK_OF_YEAR</code> fields, <code>Calendar</code> must determine the
 * first week of the month or year as a reference point.  The first week of a
 * month or year is defined as the earliest seven day period beginning on
 * <code>getFirstDayOfWeek()</code> and containing at least
 * <code>getMinimalDaysInFirstWeek()</code> days of that month or year.  Weeks
 * numbered ..., -1, 0 precede the first week; weeks numbered 2, 3,... follow
 * it.  Note that the normalized numbering returned by <code>get()</code> may be
 * different.  For example, a specific <code>Calendar</code> subclass may
 * designate the week before week 1 of a year as week <code><i>n</i></code> of
 * the previous year.
 *
 * <h4>Calendar Fields Resolution</h4>
 *
 * When computing a date and time from the calendar fields, there
 * may be insufficient information for the computation (such as only
 * year and month with no day of month), or there may be inconsistent
 * information (such as Tuesday, July 15, 1996 (Gregorian) -- July 15,
 * 1996 is actually a Monday). <code>Calendar</code> will resolve
 * calendar field values to determine the date and time in the
 * following way.
 *
 * <p><a id="resolution">If there is any conflict in calendar field values,
 * <code>Calendar</code> gives priorities to calendar fields that have been set
 * more recently.</a> The following are the default combinations of the
 * calendar fields. The most recent combination, as determined by the
 * most recently set single field, will be used.
 *
 * <p><a id="date_resolution">For the date fields</a>:
 * <blockquote>
 * <pre>
 * YEAR + MONTH + DAY_OF_MONTH
 * YEAR + MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
 * YEAR + MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
 * YEAR + DAY_OF_YEAR
 * YEAR + DAY_OF_WEEK + WEEK_OF_YEAR
 * </pre></blockquote>
 *
 * <a id="time_resolution">For the time of day fields</a>:
 * <blockquote>
 * <pre>
 * HOUR_OF_DAY
 * AM_PM + HOUR
 * </pre></blockquote>
 *
 * <p>If there are any calendar fields whose values haven't been set in the selected
 * field combination, <code>Calendar</code> uses their default values. The default
 * value of each field may vary by concrete calendar systems. For example, in
 * <code>GregorianCalendar</code>, the default of a field is the same as that
 * of the start of the Epoch: i.e., <code>YEAR = 1970</code>, <code>MONTH =
 * JANUARY</code>, <code>DAY_OF_MONTH = 1</code>, etc.
 *
 * <p>
 * <strong>Note:</strong> There are certain possible ambiguities in
 * interpretation of certain singular times, which are resolved in the
 * following ways:
 * <ol>
 *     <li> 23:59 is the last minute of the day and 00:00 is the first
 *          minute of the next day. Thus, 23:59 on Dec 31, 1999 &lt; 00:00 on
 *          Jan 1, 2000 &lt; 00:01 on Jan 1, 2000.
 *
 *     <li> Although historically not precise, midnight also belongs to "am",
 *          and noon belongs to "pm", so on the same day,
 *          12:00 am (midnight) &lt; 12:01 am, and 12:00 pm (noon) &lt; 12:01 pm
 * </ol>
 *
 * <p>
 * The date or time format strings are not part of the definition of a
 * calendar, as those must be modifiable or overridable by the user at
 * runtime. Use {@link DateFormat}
 * to format dates.
 *
 * <h4>Field Manipulation</h4>
 *
 * The calendar fields can be changed using three methods:
 * <code>set()</code>, <code>add()</code>, and <code>roll()</code>.
 *
 * <p><strong><code>set(f, value)</code></strong> changes calendar field
 * <code>f</code> to <code>value</code>.  In addition, it sets an
 * internal member variable to indicate that calendar field <code>f</code> has
 * been changed. Although calendar field <code>f</code> is changed immediately,
 * the calendar's time value in milliseconds is not recomputed until the next call to
 * <code>get()</code>, <code>getTime()</code>, <code>getTimeInMillis()</code>,
 * <code>add()</code>, or <code>roll()</code> is made. Thus, multiple calls to
 * <code>set()</code> do not trigger multiple, unnecessary
 * computations. As a result of changing a calendar field using
 * <code>set()</code>, other calendar fields may also change, depending on the
 * calendar field, the calendar field value, and the calendar system. In addition,
 * <code>get(f)</code> will not necessarily return <code>value</code> set by
 * the call to the <code>set</code> method
 * after the calendar fields have been recomputed. The specifics are determined by
 * the concrete calendar class.</p>
 *
 * <p><em>Example</em>: Consider a <code>GregorianCalendar</code>
 * originally set to August 31, 1999. Calling <code>set(Calendar.MONTH,
 * Calendar.SEPTEMBER)</code> sets the date to September 31,
 * 1999. This is a temporary internal representation that resolves to
 * October 1, 1999 if <code>getTime()</code>is then called. However, a
 * call to <code>set(Calendar.DAY_OF_MONTH, 30)</code> before the call to
 * <code>getTime()</code> sets the date to September 30, 1999, since
 * no recomputation occurs after <code>set()</code> itself.</p>
 *
 * <p><strong><code>add(f, delta)</code></strong> adds <code>delta</code>
 * to field <code>f</code>.  This is equivalent to calling <code>set(f,
 * get(f) + delta)</code> with two adjustments:</p>
 *
 * <blockquote>
 *   <p><strong>Add rule 1</strong>. The value of field <code>f</code>
 *   after the call minus the value of field <code>f</code> before the
 *   call is <code>delta</code>, modulo any overflow that has occurred in
 *   field <code>f</code>. Overflow occurs when a field value exceeds its
 *   range and, as a result, the next larger field is incremented or
 *   decremented and the field value is adjusted back into its range.</p>
 *
 *   <p><strong>Add rule 2</strong>. If a smaller field is expected to be
 *   invariant, but it is impossible for it to be equal to its
 *   prior value because of changes in its minimum or maximum after field
 *   <code>f</code> is changed or other constraints, such as time zone
 *   offset changes, then its value is adjusted to be as close
 *   as possible to its expected value. A smaller field represents a
 *   smaller unit of time. <code>HOUR</code> is a smaller field than
 *   <code>DAY_OF_MONTH</code>. No adjustment is made to smaller fields
 *   that are not expected to be invariant. The calendar system
 *   determines what fields are expected to be invariant.</p>
 * </blockquote>
 *
 * <p>In addition, unlike <code>set()</code>, <code>add()</code> forces
 * an immediate recomputation of the calendar's milliseconds and all
 * fields.</p>
 *
 * <p><em>Example</em>: Consider a <code>GregorianCalendar</code>
 * originally set to August 31, 1999. Calling <code>add(Calendar.MONTH,
 * 13)</code> sets the calendar to September 30, 2000. <strong>Add rule
 * 1</strong> sets the <code>MONTH</code> field to September, since
 * adding 13 months to August gives September of the next year. Since
 * <code>DAY_OF_MONTH</code> cannot be 31 in September in a
 * <code>GregorianCalendar</code>, <strong>add rule 2</strong> sets the
 * <code>DAY_OF_MONTH</code> to 30, the closest possible value. Although
 * it is a smaller field, <code>DAY_OF_WEEK</code> is not adjusted by
 * rule 2, since it is expected to change when the month changes in a
 * <code>GregorianCalendar</code>.</p>
 *
 * <p><strong><code>roll(f, delta)</code></strong> adds
 * <code>delta</code> to field <code>f</code> without changing larger
 * fields. This is equivalent to calling <code>add(f, delta)</code> with
 * the following adjustment:</p>
 *
 * <blockquote>
 *   <p><strong>Roll rule</strong>. Larger fields are unchanged after the
 *   call. A larger field represents a larger unit of
 *   time. <code>DAY_OF_MONTH</code> is a larger field than
 *   <code>HOUR</code>.</p>
 * </blockquote>
 *
 * <p><em>Example</em>: See {@link java.util.GregorianCalendar#roll(int, int)}.
 *
 * <p><strong>Usage model</strong>. To motivate the behavior of
 * <code>add()</code> and <code>roll()</code>, consider a user interface
 * component with increment and decrement buttons for the month, day, and
 * year, and an underlying <code>GregorianCalendar</code>. If the
 * interface reads January 31, 1999 and the user presses the month
 * increment button, what should it read? If the underlying
 * implementation uses <code>set()</code>, it might read March 3, 1999. A
 * better result would be February 28, 1999. Furthermore, if the user
 * presses the month increment button again, it should read March 31,
 * 1999, not March 28, 1999. By saving the original date and using either
 * <code>add()</code> or <code>roll()</code>, depending on whether larger
 * fields should be affected, the user interface can behave as most users
 * will intuitively expect.</p>
 *
 * @see          java.lang.System#currentTimeMillis()
 * @see          LocalDateTime
 * @see          GregorianCalendar
 * @see          TimeZone
 * @see          java.text.DateFormat
 * @author Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu
 * @since 1.1
 */

import hunt.stream.Common;
import hunt.Functions;
import hunt.util.Common;
import std.datetime : TimeZone ;


alias HuntCalendar = Calendar;

abstract class Calendar : Cloneable, Comparable!(Calendar) { // Serializable, 

    // Data flow in Calendar
    // ---------------------

    // The current time is represented in two ways by Calendar: as UTC
    // milliseconds from the epoch (1 January 1970 0:00 UTC), and as local
    // fields such as MONTH, HOUR, AM_PM, etc.  It is possible to compute the
    // millis from the fields, and vice versa.  The data needed to do this
    // conversion is encapsulated by a TimeZone object owned by the Calendar.
    // The data provided by the TimeZone object may also be overridden if the
    // user sets the ZONE_OFFSET and/or DST_OFFSET fields directly. The class
    // keeps track of what information was most recently set by the caller, and
    // uses that to compute any other information as needed.

    // If the user sets the fields using set(), the data flow is as follows.
    // This is implemented by the Calendar subclass's computeTime() method.
    // During this process, certain fields may be ignored.  The disambiguation
    // algorithm for resolving which fields to pay attention to is described
    // in the class documentation.

    //   local fields (YEAR, MONTH, DATE, HOUR, MINUTE, etc.)
    //           |
    //           | Using Calendar-specific algorithm
    //           V
    //   local standard millis
    //           |
    //           | Using TimeZone or user-set ZONE_OFFSET / DST_OFFSET
    //           V
    //   UTC millis (in time data member)

    // If the user sets the UTC millis using setTime() or setTimeInMillis(),
    // the data flow is as follows.  This is implemented by the Calendar
    // subclass's computeFields() method.

    //   UTC millis (in time data member)
    //           |
    //           | Using TimeZone getOffset()
    //           V
    //   local standard millis
    //           |
    //           | Using Calendar-specific algorithm
    //           V
    //   local fields (YEAR, MONTH, DATE, HOUR, MINUTE, etc.)

    // In general, a round trip from fields, through local and UTC millis, and
    // back out to fields is made when necessary.  This is implemented by the
    // complete() method.  Resolving a partial set of fields into a UTC millis
    // value allows all remaining fields to be generated from that value.  If
    // the Calendar is lenient, the fields are also renormalized to standard
    // ranges when they are regenerated.

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * era, e.g., AD or BC in the Julian calendar. This is a calendar-specific
     * value; see subclass documentation.
     *
     * @see GregorianCalendar#AD
     * @see GregorianCalendar#BC
     */
    enum int ERA = 0;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * year. This is a calendar-specific value; see subclass documentation.
     */
    enum int YEAR = 1;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * month. This is a calendar-specific value. The first month of
     * the year in the Gregorian and Julian calendars is
     * <code>JANUARY</code> which is 0; the last depends on the number
     * of months in a year.
     *
     * @see #JANUARY
     * @see #FEBRUARY
     * @see #MARCH
     * @see #APRIL
     * @see #MAY
     * @see #JUNE
     * @see #JULY
     * @see #AUGUST
     * @see #SEPTEMBER
     * @see #OCTOBER
     * @see #NOVEMBER
     * @see #DECEMBER
     * @see #UNDECIMBER
     */
    enum int MONTH = 2;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * week number within the current year.  The first week of the year, as
     * defined by <code>getFirstDayOfWeek()</code> and
     * <code>getMinimalDaysInFirstWeek()</code>, has value 1.  Subclasses define
     * the value of <code>WEEK_OF_YEAR</code> for days before the first week of
     * the year.
     *
     * @see #getFirstDayOfWeek
     * @see #getMinimalDaysInFirstWeek
     */
    enum int WEEK_OF_YEAR = 3;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * week number within the current month.  The first week of the month, as
     * defined by <code>getFirstDayOfWeek()</code> and
     * <code>getMinimalDaysInFirstWeek()</code>, has value 1.  Subclasses define
     * the value of <code>WEEK_OF_MONTH</code> for days before the first week of
     * the month.
     *
     * @see #getFirstDayOfWeek
     * @see #getMinimalDaysInFirstWeek
     */
    enum int WEEK_OF_MONTH = 4;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * day of the month. This is a synonym for <code>DAY_OF_MONTH</code>.
     * The first day of the month has value 1.
     *
     * @see #DAY_OF_MONTH
     */
    enum int DATE = 5;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * day of the month. This is a synonym for <code>DATE</code>.
     * The first day of the month has value 1.
     *
     * @see #DATE
     */
    enum int DAY_OF_MONTH = 5;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the day
     * number within the current year.  The first day of the year has value 1.
     */
    enum int DAY_OF_YEAR = 6;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the day
     * of the week.  This field takes values <code>SUNDAY</code>,
     * <code>MONDAY</code>, <code>TUESDAY</code>, <code>WEDNESDAY</code>,
     * <code>THURSDAY</code>, <code>FRIDAY</code>, and <code>SATURDAY</code>.
     *
     * @see #SUNDAY
     * @see #MONDAY
     * @see #TUESDAY
     * @see #WEDNESDAY
     * @see #THURSDAY
     * @see #FRIDAY
     * @see #SATURDAY
     */
    enum int DAY_OF_WEEK = 7;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * ordinal number of the day of the week within the current month. Together
     * with the <code>DAY_OF_WEEK</code> field, this uniquely specifies a day
     * within a month.  Unlike <code>WEEK_OF_MONTH</code> and
     * <code>WEEK_OF_YEAR</code>, this field's value does <em>not</em> depend on
     * <code>getFirstDayOfWeek()</code> or
     * <code>getMinimalDaysInFirstWeek()</code>.  <code>DAY_OF_MONTH 1</code>
     * through <code>7</code> always correspond to <code>DAY_OF_WEEK_IN_MONTH
     * 1</code>; <code>8</code> through <code>14</code> correspond to
     * <code>DAY_OF_WEEK_IN_MONTH 2</code>, and so on.
     * <code>DAY_OF_WEEK_IN_MONTH 0</code> indicates the week before
     * <code>DAY_OF_WEEK_IN_MONTH 1</code>.  Negative values count back from the
     * end of the month, so the last Sunday of a month is specified as
     * <code>DAY_OF_WEEK = SUNDAY, DAY_OF_WEEK_IN_MONTH = -1</code>.  Because
     * negative values count backward they will usually be aligned differently
     * within the month than positive values.  For example, if a month has 31
     * days, <code>DAY_OF_WEEK_IN_MONTH -1</code> will overlap
     * <code>DAY_OF_WEEK_IN_MONTH 5</code> and the end of <code>4</code>.
     *
     * @see #DAY_OF_WEEK
     * @see #WEEK_OF_MONTH
     */
    enum int DAY_OF_WEEK_IN_MONTH = 8;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating
     * whether the <code>HOUR</code> is before or after noon.
     * E.g., at 10:04:15.250 PM the <code>AM_PM</code> is <code>PM</code>.
     *
     * @see #AM
     * @see #PM
     * @see #HOUR
     */
    enum int AM_PM = 9;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * hour of the morning or afternoon. <code>HOUR</code> is used for the
     * 12-hour clock (0 - 11). Noon and midnight are represented by 0, not by 12.
     * E.g., at 10:04:15.250 PM the <code>HOUR</code> is 10.
     *
     * @see #AM_PM
     * @see #HOUR_OF_DAY
     */
    enum int HOUR = 10;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * hour of the day. <code>HOUR_OF_DAY</code> is used for the 24-hour clock.
     * E.g., at 10:04:15.250 PM the <code>HOUR_OF_DAY</code> is 22.
     *
     * @see #HOUR
     */
    enum int HOUR_OF_DAY = 11;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * minute within the hour.
     * E.g., at 10:04:15.250 PM the <code>MINUTE</code> is 4.
     */
    enum int MINUTE = 12;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * second within the minute.
     * E.g., at 10:04:15.250 PM the <code>SECOND</code> is 15.
     */
    enum int SECOND = 13;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * millisecond within the second.
     * E.g., at 10:04:15.250 PM the <code>MILLISECOND</code> is 250.
     */
    enum int MILLISECOND = 14;

    /**
     * Field number for <code>get</code> and <code>set</code>
     * indicating the raw offset from GMT in milliseconds.
     * <p>
     * This field reflects the correct GMT offset value of the time
     * zone of this <code>Calendar</code> if the
     * <code>TimeZone</code> implementation subclass supports
     * historical GMT offset changes.
     */
    enum int ZONE_OFFSET = 15;

    /**
     * Field number for <code>get</code> and <code>set</code> indicating the
     * daylight saving offset in milliseconds.
     * <p>
     * This field reflects the correct daylight saving offset value of
     * the time zone of this <code>Calendar</code> if the
     * <code>TimeZone</code> implementation subclass supports
     * historical Daylight Saving Time schedule changes.
     */
    enum int DST_OFFSET = 16;

    /**
     * The number of distinct fields recognized by <code>get</code> and <code>set</code>.
     * Field numbers range from <code>0..FIELD_COUNT-1</code>.
     */
    enum int FIELD_COUNT = 17;

    /**
     * Value of the {@link #DAY_OF_WEEK} field indicating
     * Sunday.
     */
    enum int SUNDAY = 1;

    /**
     * Value of the {@link #DAY_OF_WEEK} field indicating
     * Monday.
     */
    enum int MONDAY = 2;

    /**
     * Value of the {@link #DAY_OF_WEEK} field indicating
     * Tuesday.
     */
    enum int TUESDAY = 3;

    /**
     * Value of the {@link #DAY_OF_WEEK} field indicating
     * Wednesday.
     */
    enum int WEDNESDAY = 4;

    /**
     * Value of the {@link #DAY_OF_WEEK} field indicating
     * Thursday.
     */
    enum int THURSDAY = 5;

    /**
     * Value of the {@link #DAY_OF_WEEK} field indicating
     * Friday.
     */
    enum int FRIDAY = 6;

    /**
     * Value of the {@link #DAY_OF_WEEK} field indicating
     * Saturday.
     */
    enum int SATURDAY = 7;

    /**
     * Value of the {@link #MONTH} field indicating the
     * first month of the year in the Gregorian and Julian calendars.
     */
    enum int JANUARY = 0;

    /**
     * Value of the {@link #MONTH} field indicating the
     * second month of the year in the Gregorian and Julian calendars.
     */
    enum int FEBRUARY = 1;

    /**
     * Value of the {@link #MONTH} field indicating the
     * third month of the year in the Gregorian and Julian calendars.
     */
    enum int MARCH = 2;

    /**
     * Value of the {@link #MONTH} field indicating the
     * fourth month of the year in the Gregorian and Julian calendars.
     */
    enum int APRIL = 3;

    /**
     * Value of the {@link #MONTH} field indicating the
     * fifth month of the year in the Gregorian and Julian calendars.
     */
    enum int MAY = 4;

    /**
     * Value of the {@link #MONTH} field indicating the
     * sixth month of the year in the Gregorian and Julian calendars.
     */
    enum int JUNE = 5;

    /**
     * Value of the {@link #MONTH} field indicating the
     * seventh month of the year in the Gregorian and Julian calendars.
     */
    enum int JULY = 6;

    /**
     * Value of the {@link #MONTH} field indicating the
     * eighth month of the year in the Gregorian and Julian calendars.
     */
    enum int AUGUST = 7;

    /**
     * Value of the {@link #MONTH} field indicating the
     * ninth month of the year in the Gregorian and Julian calendars.
     */
    enum int SEPTEMBER = 8;

    /**
     * Value of the {@link #MONTH} field indicating the
     * tenth month of the year in the Gregorian and Julian calendars.
     */
    enum int OCTOBER = 9;

    /**
     * Value of the {@link #MONTH} field indicating the
     * eleventh month of the year in the Gregorian and Julian calendars.
     */
    enum int NOVEMBER = 10;

    /**
     * Value of the {@link #MONTH} field indicating the
     * twelfth month of the year in the Gregorian and Julian calendars.
     */
    enum int DECEMBER = 11;

    /**
     * Value of the {@link #MONTH} field indicating the
     * thirteenth month of the year. Although <code>GregorianCalendar</code>
     * does not use this value, lunar calendars do.
     */
    enum int UNDECIMBER = 12;

    /**
     * Value of the {@link #AM_PM} field indicating the
     * period of the day from midnight to just before noon.
     */
    enum int AM = 0;

    /**
     * Value of the {@link #AM_PM} field indicating the
     * period of the day from noon to just before midnight.
     */
    enum int PM = 1;

    /**
     * A style specifier for {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} indicating names in all styles, such as
     * "January" and "Jan".
     *
     * @see #SHORT_FORMAT
     * @see #LONG_FORMAT
     * @see #SHORT_STANDALONE
     * @see #LONG_STANDALONE
     * @see #SHORT
     * @see #LONG
     * @since 1.6
     */
    enum int ALL_STYLES = 0;

    enum int STANDALONE_MASK = 0x8000;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} equivalent to {@link #SHORT_FORMAT}.
     *
     * @see #SHORT_STANDALONE
     * @see #LONG
     * @since 1.6
     */
    enum int SHORT = 1;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} equivalent to {@link #LONG_FORMAT}.
     *
     * @see #LONG_STANDALONE
     * @see #SHORT
     * @since 1.6
     */
    enum int LONG = 2;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} indicating a narrow name used for format. Narrow names
     * are typically single character strings, such as "M" for Monday.
     *
     * @see #NARROW_STANDALONE
     * @see #SHORT_FORMAT
     * @see #LONG_FORMAT
     * @since 1.8
     */
    enum int NARROW_FORMAT = 4;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} indicating a narrow name independently. Narrow names
     * are typically single character strings, such as "M" for Monday.
     *
     * @see #NARROW_FORMAT
     * @see #SHORT_STANDALONE
     * @see #LONG_STANDALONE
     * @since 1.8
     */
    enum int NARROW_STANDALONE = NARROW_FORMAT | STANDALONE_MASK;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} indicating a short name used for format.
     *
     * @see #SHORT_STANDALONE
     * @see #LONG_FORMAT
     * @see #LONG_STANDALONE
     * @since 1.8
     */
    enum int SHORT_FORMAT = 1;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} indicating a long name used for format.
     *
     * @see #LONG_STANDALONE
     * @see #SHORT_FORMAT
     * @see #SHORT_STANDALONE
     * @since 1.8
     */
    enum int LONG_FORMAT = 2;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} indicating a short name used independently,
     * such as a month abbreviation as calendar headers.
     *
     * @see #SHORT_FORMAT
     * @see #LONG_FORMAT
     * @see #LONG_STANDALONE
     * @since 1.8
     */
    enum int SHORT_STANDALONE = SHORT | STANDALONE_MASK;

    /**
     * A style specifier for {@link #getDisplayName(int, int, Locale)
     * getDisplayName} and {@link #getDisplayNames(int, int, Locale)
     * getDisplayNames} indicating a long name used independently,
     * such as a month name as calendar headers.
     *
     * @see #LONG_FORMAT
     * @see #SHORT_FORMAT
     * @see #SHORT_STANDALONE
     * @since 1.8
     */
    enum int LONG_STANDALONE = LONG | STANDALONE_MASK;

    // Internal notes:
    // Calendar contains two kinds of time representations: current "time" in
    // milliseconds, and a set of calendar "fields" representing the current time.
    // The two representations are usually in sync, but can get out of sync
    // as follows.
    // 1. Initially, no fields are set, and the time is invalid.
    // 2. If the time is set, all fields are computed and in sync.
    // 3. If a single field is set, the time is invalid.
    // Recomputation of the time and fields happens when the object needs
    // to return a result to the user, or use a result for a computation.

    /**
     * The calendar field values for the currently set time for this calendar.
     * This is an array of <code>FIELD_COUNT</code> integers, with index values
     * <code>ERA</code> through <code>DST_OFFSET</code>.
     * @serial
     */
    //@SuppressWarnings("ProtectedField")
    protected int[]           fields;

    /**
     * The flags which tell if a specified calendar field for the calendar is set.
     * A new object has no fields set.  After the first call to a method
     * which generates the fields, they all remain set after that.
     * This is an array of <code>FIELD_COUNT</code> bools, with index values
     * <code>ERA</code> through <code>DST_OFFSET</code>.
     * @serial
     */
    //@SuppressWarnings("ProtectedField")
    protected bool[]       isSet;

    /**
     * Pseudo-time-stamps which specify when each field was set. There
     * are two special values, UNSET and COMPUTED. Values from
     * MINIMUM_USER_SET to Integer.MAX_VALUE are legal user set values.
     */
    private  int[]   stamp;

    /**
     * The currently set time for this calendar, expressed in milliseconds after
     * January 1, 1970, 0:00:00 GMT.
     * @see #isTimeSet
     * @serial
     */
    //@SuppressWarnings("ProtectedField")
    protected long          time;

    /**
     * True if then the value of <code>time</code> is valid.
     * The time is made invalid by a change to an item of <code>field[]</code>.
     * @see #time
     * @serial
     */
    //@SuppressWarnings("ProtectedField")
    protected bool       isTimeSet;

    /**
     * True if <code>fields[]</code> are in sync with the currently set time.
     * If false, then the next attempt to get the value of a field will
     * force a recomputation of all fields from the current value of
     * <code>time</code>.
     * @serial
     */
    //@SuppressWarnings("ProtectedField")
    protected bool       areFieldsSet;

    /**
     * True if all fields have been set.
     * @serial
     */
     bool       areAllFieldsSet;

    /**
     * <code>True</code> if this calendar allows out-of-range field values during computation
     * of <code>time</code> from <code>fields[]</code>.
     * @see #setLenient
     * @see #isLenient
     * @serial
     */
    private bool         lenient = true;

    /**
     * The <code>TimeZone</code> used by this calendar. <code>Calendar</code>
     * uses the time zone data to translate between locale and GMT time.
     * @serial
     */
    private TimeZone        zone;

    /**
     * <code>True</code> if zone references to a shared TimeZone object.
     */
    private  bool sharedZone = false;

    /**
     * The first day of the week, with possible values <code>SUNDAY</code>,
     * <code>MONDAY</code>, etc.  This is a locale-dependent value.
     * @serial
     */
    private int             firstDayOfWeek;

    /**
     * The number of days required for the first week in a month or year,
     * with possible values from 1 to 7.  This is a locale-dependent value.
     * @serial
     */
    private int             minimalDaysInFirstWeek;

    /**
     * Cache to hold the firstDayOfWeek and minimalDaysInFirstWeek
     * of a Locale.
     */
    // private enum ConcurrentMap!(Locale, int[]) cachedLocaleData
    //     = new ConcurrentHashMap(3);

    // __gshared  Map!(Locale, int[]) cachedLocaleData;
    // Special values of stamp[]
    /**
     * The corresponding fields[] has no value.
     */
    private enum int        UNSET = 0;

    /**
     * The value of the corresponding fields[] has been calculated internally.
     */
    private enum int        COMPUTED = 1;

    /**
     * The value of the corresponding fields[] has been set externally. Stamp
     * values which are greater than 1 represents the (pseudo) time when the
     * corresponding fields[] value was set.
     */
    private enum int        MINIMUM_USER_STAMP = 2;

    /**
     * The mask value that represents all of the fields.
     */
    enum int ALL_FIELDS = (1 << FIELD_COUNT) - 1;

    /**
     * The next available value for <code>stamp[]</code>, an internal array.
     * This actually should not be written out to the stream, and will probably
     * be removed from the stream in the near future.  In the meantime,
     * a value of <code>MINIMUM_USER_STAMP</code> should be used.
     * @serial
     */
    private int             nextStamp = MINIMUM_USER_STAMP;

    // the internal serial version which says which version was written
    // - 0 (default) for version up to JDK 1.1.5
    // - 1 for version from JDK 1.1.6, which writes a correct 'time' value
    //     as well as compatible values for other fields.  This is a
    //     transitional format.
    // - 2 (not implemented yet) a future version, in which fields[],
    //     areFieldsSet, and isTimeSet become , and isSet[] is
    //     removed. In JDK 1.1.6 we write a format compatible with version 2.
    enum int        currentSerialVersion = 1;

    /**
     * The version of the serialized data on the stream.  Possible values:
     * <dl>
     * <dt><b>0</b> or not present on stream</dt>
     * <dd>
     * JDK 1.1.5 or earlier.
     * </dd>
     * <dt><b>1</b></dt>
     * <dd>
     * JDK 1.1.6 or later.  Writes a correct 'time' value
     * as well as compatible values for other fields.  This is a
     * transitional format.
     * </dd>
     * </dl>
     * When streaming out this class, the most recent format
     * and the highest allowable <code>serialVersionOnStream</code>
     * is written.
     * @serial
     * @since 1.1.6
     */
    private int             serialVersionOnStream = currentSerialVersion;

    // Mask values for calendar fields
    //@SuppressWarnings("PointlessBitwiseExpression")
    enum int ERA_MASK           = (1 << ERA);
    enum int YEAR_MASK          = (1 << YEAR);
    enum int MONTH_MASK         = (1 << MONTH);
    enum int WEEK_OF_YEAR_MASK  = (1 << WEEK_OF_YEAR);
    enum int WEEK_OF_MONTH_MASK = (1 << WEEK_OF_MONTH);
    enum int DAY_OF_MONTH_MASK  = (1 << DAY_OF_MONTH);
    enum int DATE_MASK          = DAY_OF_MONTH_MASK;
    enum int DAY_OF_YEAR_MASK   = (1 << DAY_OF_YEAR);
    enum int DAY_OF_WEEK_MASK   = (1 << DAY_OF_WEEK);
    enum int DAY_OF_WEEK_IN_MONTH_MASK  = (1 << DAY_OF_WEEK_IN_MONTH);
    enum int AM_PM_MASK         = (1 << AM_PM);
    enum int HOUR_MASK          = (1 << HOUR);
    enum int HOUR_OF_DAY_MASK   = (1 << HOUR_OF_DAY);
    enum int MINUTE_MASK        = (1 << MINUTE);
    enum int SECOND_MASK        = (1 << SECOND);
    enum int MILLISECOND_MASK   = (1 << MILLISECOND);
    enum int ZONE_OFFSET_MASK   = (1 << ZONE_OFFSET);
    enum int DST_OFFSET_MASK    = (1 << DST_OFFSET);

    // shared static this()
    // {
        // cachedLocaleData = new HashMap!(Locale, int[])(3);
        mixin(MakeGlobalVar!(Map!(Locale, int[]))("cachedLocaleData",`new HashMap!(Locale, int[])(3)`));
    // }

    /**
     * {@code Calendar.Builder} is used for creating a {@code Calendar} from
     * various date-time parameters.
     *
     * <p>There are two ways to set a {@code Calendar} to a date-time value. One
     * is to set the instant parameter to a millisecond offset from the <a
     * href="Calendar.html#Epoch">Epoch</a>. The other is to set individual
     * field parameters, such as {@link Calendar#YEAR YEAR}, to their desired
     * values. These two ways can't be mixed. Trying to set both the instant and
     * individual fields will cause an {@link IllegalStateException} to be
     * thrown. However, it is permitted to override previous values of the
     * instant or field parameters.
     *
     * <p>If no enough field parameters are given for determining date and/or
     * time, calendar specific default values are used when building a
     * {@code Calendar}. For example, if the {@link Calendar#YEAR YEAR} value
     * isn't given for the Gregorian calendar, 1970 will be used. If there are
     * any conflicts among field parameters, the <a
     * href="Calendar.html#resolution"> resolution rules</a> are applied.
     * Therefore, the order of field setting matters.
     *
     * <p>In addition to the date-time parameters,
     * the {@linkplain #setLocale(Locale) locale},
     * {@linkplain #setTimeZone(TimeZone) time zone},
     * {@linkplain #setWeekDefinition(int, int) week definition}, and
     * {@linkplain #setLenient(bool) leniency mode} parameters can be set.
     *
     * <p><b>Examples</b>
     * <p>The following are sample usages. Sample code assumes that the
     * {@code Calendar} constants are statically imported.
     *
     * <p>The following code produces a {@code Calendar} with date 2012-12-31
     * (Gregorian) because Monday is the first day of a week with the <a
     * href="GregorianCalendar.html#iso8601_compatible_setting"> ISO 8601
     * compatible week parameters</a>.
     * <pre>
     *   Calendar cal = new Calendar.Builder().setCalendarType("iso8601")
     *                        .setWeekDate(2013, 1, MONDAY).build();</pre>
     * <p>The following code produces a Japanese {@code Calendar} with date
     * 1989-01-08 (Gregorian), assuming that the default {@link Calendar#ERA ERA}
     * is <em>Heisei</em> that started on that day.
     * <pre>
     *   Calendar cal = new Calendar.Builder().setCalendarType("japanese")
     *                        .setFields(YEAR, 1, DAY_OF_YEAR, 1).build();</pre>
     *
     * @since 1.8
     * @see Calendar#getInstance(TimeZone, Locale)
     * @see Calendar#fields
     */
    // static class Builder {
    //     private enum int NFIELDS = FIELD_COUNT + 1; // +1 for WEEK_YEAR
    //     private enum int WEEK_YEAR = FIELD_COUNT;

    //     private long instant;
    //     // Calendar.stamp[] (lower half) and Calendar.fields[] (upper half) combined
    //     private int[] fields;
    //     // Pseudo timestamp starting from MINIMUM_USER_STAMP.
    //     // (COMPUTED is used to indicate that the instant has been set.)
    //     private int nextStamp;
    //     // maxFieldIndex keeps the max index of fields which have been set.
    //     // (WEEK_YEAR is never included.)
    //     private int maxFieldIndex;
    //     private String type;
    //     private TimeZone zone;
    //     private bool lenient = true;
    //     private Locale locale;
    //     private int firstDayOfWeek, minimalDaysInFirstWeek;

    //     /**
    //      * Constructs a {@code Calendar.Builder}.
    //      */
    //     this() {
    //     }

    //     /**
    //      * Sets the instant parameter to the given {@code instant} value that is
    //      * a millisecond offset from <a href="Calendar.html#Epoch">the
    //      * Epoch</a>.
    //      *
    //      * @param instant a millisecond offset from the Epoch
    //      * @return this {@code Calendar.Builder}
    //      * @throws IllegalStateException if any of the field parameters have
    //      *                               already been set
    //      * @see Calendar#setTime(LocalDateTime)
    //      * @see Calendar#setTimeInMillis(long)
    //      * @see Calendar#time
    //      */
    //     Builder setInstant(long instant) {
    //         if (fields !is null) {
    //             throw new IllegalStateException();
    //         }
    //         this.instant = instant;
    //         nextStamp = COMPUTED;
    //         return this;
    //     }

    //     /**
    //      * Sets the instant parameter to the {@code instant} value given by a
    //      * {@link LocalDateTime}. This method is equivalent to a call to
    //      * {@link #setInstant(long) setInstant(instant.getTime())}.
    //      *
    //      * @param instant a {@code LocalDateTime} representing a millisecond offset from
    //      *                the Epoch
    //      * @return this {@code Calendar.Builder}
    //      * @throws NullPointerException  if {@code instant} is {@code null}
    //      * @throws IllegalStateException if any of the field parameters have
    //      *                               already been set
    //      * @see Calendar#setTime(LocalDateTime)
    //      * @see Calendar#setTimeInMillis(long)
    //      * @see Calendar#time
    //      */
    //     Builder setInstant(LocalDateTime instant) {
    //         return setInstant(instant.getTime()); // NPE if instant is null
    //     }

    //     /**
    //      * Sets the {@code field} parameter to the given {@code value}.
    //      * {@code field} is an index to the {@link Calendar#fields}, such as
    //      * {@link Calendar#DAY_OF_MONTH DAY_OF_MONTH}. Field value validation is
    //      * not performed in this method. Any out of range values are either
    //      * normalized in lenient mode or detected as an invalid value in
    //      * non-lenient mode when building a {@code Calendar}.
    //      *
    //      * @param field an index to the {@code Calendar} fields
    //      * @param value the field value
    //      * @return this {@code Calendar.Builder}
    //      * @throws IllegalArgumentException if {@code field} is invalid
    //      * @throws IllegalStateException if the instant value has already been set,
    //      *                      or if fields have been set too many
    //      *                      (approximately {@link Integer#MAX_VALUE}) times.
    //      * @see Calendar#set(int, int)
    //      */
    //     Builder set(int field, int value) {
    //         // Note: WEEK_YEAR can't be set with this method.
    //         if (field < 0 || field >= FIELD_COUNT) {
    //             throw new IllegalArgumentException("field is invalid");
    //         }
    //         if (isInstantSet()) {
    //             throw new IllegalStateException("instant has been set");
    //         }
    //         allocateFields();
    //         internalSet(field, value);
    //         return this;
    //     }

    //     /**
    //      * Sets field parameters to their values given by
    //      * {@code fieldValuePairs} that are pairs of a field and its value.
    //      * For example,
    //      * <pre>
    //      *   setFields(Calendar.YEAR, 2013,
    //      *             Calendar.MONTH, Calendar.DECEMBER,
    //      *             Calendar.DAY_OF_MONTH, 23);</pre>
    //      * is equivalent to the sequence of the following
    //      * {@link #set(int, int) set} calls:
    //      * <pre>
    //      *   set(Calendar.YEAR, 2013)
    //      *   .set(Calendar.MONTH, Calendar.DECEMBER)
    //      *   .set(Calendar.DAY_OF_MONTH, 23);</pre>
    //      *
    //      * @param fieldValuePairs field-value pairs
    //      * @return this {@code Calendar.Builder}
    //      * @throws NullPointerException if {@code fieldValuePairs} is {@code null}
    //      * @throws IllegalArgumentException if any of fields are invalid,
    //      *             or if {@code fieldValuePairs.length} is an odd number.
    //      * @throws IllegalStateException    if the instant value has been set,
    //      *             or if fields have been set too many (approximately
    //      *             {@link Integer#MAX_VALUE}) times.
    //      */
    //     Builder setFields(int... fieldValuePairs) {
    //         int len = fieldValuePairs.length;
    //         if ((len % 2) != 0) {
    //             throw new IllegalArgumentException();
    //         }
    //         if (isInstantSet()) {
    //             throw new IllegalStateException("instant has been set");
    //         }
    //         if ((nextStamp + len / 2) < 0) {
    //             throw new IllegalStateException("stamp counter overflow");
    //         }
    //         allocateFields();
    //         for (int i = 0; i < len; ) {
    //             int field = fieldValuePairs[i++];
    //             // Note: WEEK_YEAR can't be set with this method.
    //             if (field < 0 || field >= FIELD_COUNT) {
    //                 throw new IllegalArgumentException("field is invalid");
    //             }
    //             internalSet(field, fieldValuePairs[i++]);
    //         }
    //         return this;
    //     }

    //     /**
    //      * Sets the date field parameters to the values given by {@code year},
    //      * {@code month}, and {@code dayOfMonth}. This method is equivalent to
    //      * a call to:
    //      * <pre>
    //      *   setFields(Calendar.YEAR, year,
    //      *             Calendar.MONTH, month,
    //      *             Calendar.DAY_OF_MONTH, dayOfMonth);</pre>
    //      *
    //      * @param year       the {@link Calendar#YEAR YEAR} value
    //      * @param month      the {@link Calendar#MONTH MONTH} value
    //      *                   (the month numbering is <em>0-based</em>).
    //      * @param dayOfMonth the {@link Calendar#DAY_OF_MONTH DAY_OF_MONTH} value
    //      * @return this {@code Calendar.Builder}
    //      */
    //     Builder setDate(int year, int month, int dayOfMonth) {
    //         return setFields(YEAR, year, MONTH, month, DAY_OF_MONTH, dayOfMonth);
    //     }

    //     /**
    //      * Sets the time of day field parameters to the values given by
    //      * {@code hourOfDay}, {@code minute}, and {@code second}. This method is
    //      * equivalent to a call to:
    //      * <pre>
    //      *   setTimeOfDay(hourOfDay, minute, second, 0);</pre>
    //      *
    //      * @param hourOfDay the {@link Calendar#HOUR_OF_DAY HOUR_OF_DAY} value
    //      *                  (24-hour clock)
    //      * @param minute    the {@link Calendar#MINUTE MINUTE} value
    //      * @param second    the {@link Calendar#SECOND SECOND} value
    //      * @return this {@code Calendar.Builder}
    //      */
    //     Builder setTimeOfDay(int hourOfDay, int minute, int second) {
    //         return setTimeOfDay(hourOfDay, minute, second, 0);
    //     }

    //     /**
    //      * Sets the time of day field parameters to the values given by
    //      * {@code hourOfDay}, {@code minute}, {@code second}, and
    //      * {@code millis}. This method is equivalent to a call to:
    //      * <pre>
    //      *   setFields(Calendar.HOUR_OF_DAY, hourOfDay,
    //      *             Calendar.MINUTE, minute,
    //      *             Calendar.SECOND, second,
    //      *             Calendar.MILLISECOND, millis);</pre>
    //      *
    //      * @param hourOfDay the {@link Calendar#HOUR_OF_DAY HOUR_OF_DAY} value
    //      *                  (24-hour clock)
    //      * @param minute    the {@link Calendar#MINUTE MINUTE} value
    //      * @param second    the {@link Calendar#SECOND SECOND} value
    //      * @param millis    the {@link Calendar#MILLISECOND MILLISECOND} value
    //      * @return this {@code Calendar.Builder}
    //      */
    //     Builder setTimeOfDay(int hourOfDay, int minute, int second, int millis) {
    //         return setFields(HOUR_OF_DAY, hourOfDay, MINUTE, minute,
    //                          SECOND, second, MILLISECOND, millis);
    //     }

    //     /**
    //      * Sets the week-based date parameters to the values with the given
    //      * date specifiers - week year, week of year, and day of week.
    //      *
    //      * <p>If the specified calendar doesn't support week dates, the
    //      * {@link #build() build} method will throw an {@link IllegalArgumentException}.
    //      *
    //      * @param weekYear   the week year
    //      * @param weekOfYear the week number based on {@code weekYear}
    //      * @param dayOfWeek  the day of week value: one of the constants
    //      *     for the {@link Calendar#DAY_OF_WEEK DAY_OF_WEEK} field:
    //      *     {@link Calendar#SUNDAY SUNDAY}, ..., {@link Calendar#SATURDAY SATURDAY}.
    //      * @return this {@code Calendar.Builder}
    //      * @see Calendar#setWeekDate(int, int, int)
    //      * @see Calendar#isWeekDateSupported()
    //      */
    //     Builder setWeekDate(int weekYear, int weekOfYear, int dayOfWeek) {
    //         allocateFields();
    //         internalSet(WEEK_YEAR, weekYear);
    //         internalSet(WEEK_OF_YEAR, weekOfYear);
    //         internalSet(DAY_OF_WEEK, dayOfWeek);
    //         return this;
    //     }

    //     /**
    //      * Sets the time zone parameter to the given {@code zone}. If no time
    //      * zone parameter is given to this {@code Calendar.Builder}, the
    //      * {@linkplain TimeZone#getDefault() default
    //      * <code>TimeZone</code>} will be used in the {@link #build() build}
    //      * method.
    //      *
    //      * @param zone the {@link TimeZone}
    //      * @return this {@code Calendar.Builder}
    //      * @throws NullPointerException if {@code zone} is {@code null}
    //      * @see Calendar#setTimeZone(TimeZone)
    //      */
    //     Builder setTimeZone(TimeZone zone) {
    //         if (zone is null) {
    //             throw new NullPointerException();
    //         }
    //         this.zone = zone;
    //         return this;
    //     }

    //     /**
    //      * Sets the lenient mode parameter to the value given by {@code lenient}.
    //      * If no lenient parameter is given to this {@code Calendar.Builder},
    //      * lenient mode will be used in the {@link #build() build} method.
    //      *
    //      * @param lenient {@code true} for lenient mode;
    //      *                {@code false} for non-lenient mode
    //      * @return this {@code Calendar.Builder}
    //      * @see Calendar#setLenient(bool)
    //      */
    //     Builder setLenient(bool lenient) {
    //         this.lenient = lenient;
    //         return this;
    //     }

    //     /**
    //      * Sets the calendar type parameter to the given {@code type}. The
    //      * calendar type given by this method has precedence over any explicit
    //      * or implicit calendar type given by the
    //      * {@linkplain #setLocale(Locale) locale}.
    //      *
    //      * <p>In addition to the available calendar types returned by the
    //      * {@link Calendar#getAvailableCalendarTypes() Calendar.getAvailableCalendarTypes}
    //      * method, {@code "gregorian"} and {@code "iso8601"} as aliases of
    //      * {@code "gregory"} can be used with this method.
    //      *
    //      * @param type the calendar type
    //      * @return this {@code Calendar.Builder}
    //      * @throws NullPointerException if {@code type} is {@code null}
    //      * @throws IllegalArgumentException if {@code type} is unknown
    //      * @throws IllegalStateException if another calendar type has already been set
    //      * @see Calendar#getCalendarType()
    //      * @see Calendar#getAvailableCalendarTypes()
    //      */
    //     Builder setCalendarType(String type) {
    //         if (type.equals("gregorian")) { // NPE if type is null
    //             type = "gregory";
    //         }
    //         if (!Calendar.getAvailableCalendarTypes().contains(type)
    //                 && !type.equals("iso8601")) {
    //             throw new IllegalArgumentException("unknown calendar type: " ~ type);
    //         }
    //         if (this.type is null) {
    //             this.type = type;
    //         } else {
    //             if (!this.type.equals(type)) {
    //                 throw new IllegalStateException("calendar type override");
    //             }
    //         }
    //         return this;
    //     }

    //     /**
    //      * Sets the locale parameter to the given {@code locale}. If no locale
    //      * is given to this {@code Calendar.Builder}, the {@linkplain
    //      * Locale#getDefault(LocaleCategory) default <code>Locale</code>}
    //      * for {@link LocaleCategory#FORMAT} will be used.
    //      *
    //      * <p>If no calendar type is explicitly given by a call to the
    //      * {@link #setCalendarType(String) setCalendarType} method,
    //      * the {@code Locale} value is used to determine what type of
    //      * {@code Calendar} to be built.
    //      *
    //      * <p>If no week definition parameters are explicitly given by a call to
    //      * the {@link #setWeekDefinition(int,int) setWeekDefinition} method, the
    //      * {@code Locale}'s default values are used.
    //      *
    //      * @param locale the {@link Locale}
    //      * @throws NullPointerException if {@code locale} is {@code null}
    //      * @return this {@code Calendar.Builder}
    //      * @see Calendar#getInstance(Locale)
    //      */
    //     Builder setLocale(Locale locale) {
    //         if (locale is null) {
    //             throw new NullPointerException();
    //         }
    //         this.locale = locale;
    //         return this;
    //     }

    //     /**
    //      * Sets the week definition parameters to the values given by
    //      * {@code firstDayOfWeek} and {@code minimalDaysInFirstWeek} that are
    //      * used to determine the <a href="Calendar.html#first_week">first
    //      * week</a> of a year. The parameters given by this method have
    //      * precedence over the default values given by the
    //      * {@linkplain #setLocale(Locale) locale}.
    //      *
    //      * @param firstDayOfWeek the first day of a week; one of
    //      *                       {@link Calendar#SUNDAY} to {@link Calendar#SATURDAY}
    //      * @param minimalDaysInFirstWeek the minimal number of days in the first
    //      *                               week (1..7)
    //      * @return this {@code Calendar.Builder}
    //      * @throws IllegalArgumentException if {@code firstDayOfWeek} or
    //      *                                  {@code minimalDaysInFirstWeek} is invalid
    //      * @see Calendar#getFirstDayOfWeek()
    //      * @see Calendar#getMinimalDaysInFirstWeek()
    //      */
    //     Builder setWeekDefinition(int firstDayOfWeek, int minimalDaysInFirstWeek) {
    //         if (!isValidWeekParameter(firstDayOfWeek)
    //                 || !isValidWeekParameter(minimalDaysInFirstWeek)) {
    //             throw new IllegalArgumentException();
    //         }
    //         this.firstDayOfWeek = firstDayOfWeek;
    //         this.minimalDaysInFirstWeek = minimalDaysInFirstWeek;
    //         return this;
    //     }

    //     /**
    //      * Returns a {@code Calendar} built from the parameters set by the
    //      * setter methods. The calendar type given by the {@link #setCalendarType(String)
    //      * setCalendarType} method or the {@linkplain #setLocale(Locale) locale} is
    //      * used to determine what {@code Calendar} to be created. If no explicit
    //      * calendar type is given, the locale's default calendar is created.
    //      *
    //      * <p>If the calendar type is {@code "iso8601"}, the
    //      * {@linkplain GregorianCalendar#setGregorianChange(LocalDateTime) Gregorian change date}
    //      * of a {@link GregorianCalendar} is set to {@code LocalDateTime(Long.MIN_VALUE)}
    //      * to be the <em>proleptic</em> Gregorian calendar. Its week definition
    //      * parameters are also set to be <a
    //      * href="GregorianCalendar.html#iso8601_compatible_setting">compatible
    //      * with the ISO 8601 standard</a>. Note that the
    //      * {@link GregorianCalendar#getCalendarType() getCalendarType} method of
    //      * a {@code GregorianCalendar} created with {@code "iso8601"} returns
    //      * {@code "gregory"}.
    //      *
    //      * <p>The default values are used for locale and time zone if these
    //      * parameters haven't been given explicitly.
    //      * <p>
    //      * If the locale contains the time zone with "tz"
    //      * <a href="Locale.html#def_locale_extension">Unicode extension</a>,
    //      * and time zone hasn't been given explicitly, time zone in the locale
    //      * is used.
    //      *
    //      * <p>Any out of range field values are either normalized in lenient
    //      * mode or detected as an invalid value in non-lenient mode.
    //      *
    //      * @return a {@code Calendar} built with parameters of this {@code
    //      *         Calendar.Builder}
    //      * @throws IllegalArgumentException if the calendar type is unknown, or
    //      *             if any invalid field values are given in non-lenient mode, or
    //      *             if a week date is given for the calendar type that doesn't
    //      *             support week dates.
    //      * @see Calendar#getInstance(TimeZone, Locale)
    //      * @see Locale#getDefault(LocaleCategory)
    //      * @see TimeZone#getDefault()
    //      */
    //     Calendar build() {
    //         if (locale is null) {
    //             locale = Locale.getDefault();
    //         }
    //         if (zone is null) {
    //             zone = defaultTimeZone(locale);
    //         }
    //         Calendar cal;
    //         if (type is null) {
    //             type = locale.getUnicodeLocaleType("ca");
    //         }
    //         if (type is null) {
    //             if (locale.getCountry() == "TH"
    //                 && locale.getLanguage() == "th") {
    //                 type = "buddhist";
    //             } else {
    //                 type = "gregory";
    //             }
    //         }
    //         switch (type) {
    //         case "gregory":
    //             cal = new GregorianCalendar(zone, locale, true);
    //             break;
    //         case "iso8601":
    //             GregorianCalendar gcal = new GregorianCalendar(zone, locale, true);
    //             // make gcal a proleptic Gregorian
    //             gcal.setGregorianChange(new LocalDateTime(Long.MIN_VALUE));
    //             // and week definition to be compatible with ISO 8601
    //             setWeekDefinition(MONDAY, 4);
    //             cal = gcal;
    //             break;
    //         case "buddhist":
    //             cal = new BuddhistCalendar(zone, locale);
    //             cal.clear();
    //             break;
    //         case "japanese":
    //             cal = new JapaneseImperialCalendar(zone, locale, true);
    //             break;
    //         default:
    //             throw new IllegalArgumentException("unknown calendar type: " ~ type);
    //         }
    //         cal.setLenient(lenient);
    //         if (firstDayOfWeek != 0) {
    //             cal.setFirstDayOfWeek(firstDayOfWeek);
    //             cal.setMinimalDaysInFirstWeek(minimalDaysInFirstWeek);
    //         }
    //         if (isInstantSet()) {
    //             cal.setTimeInMillis(instant);
    //             cal.complete();
    //             return cal;
    //         }

    //         if (fields !is null) {
    //             bool weekDate = isSet(WEEK_YEAR)
    //                                    && fields[WEEK_YEAR] > fields[YEAR];
    //             if (weekDate && !cal.isWeekDateSupported()) {
    //                 throw new IllegalArgumentException("week date is unsupported by " ~ type);
    //             }

    //             // Set the fields from the min stamp to the max stamp so that
    //             // the fields resolution works in the Calendar.
    //             for (int stamp = MINIMUM_USER_STAMP; stamp < nextStamp; stamp++) {
    //                 for (int index = 0; index <= maxFieldIndex; index++) {
    //                     if (fields[index] == stamp) {
    //                         cal.set(index, fields[NFIELDS + index]);
    //                         break;
    //                     }
    //                 }
    //             }

    //             if (weekDate) {
    //                 int weekOfYear = isSet(WEEK_OF_YEAR) ? fields[NFIELDS + WEEK_OF_YEAR] : 1;
    //                 int dayOfWeek = isSet(DAY_OF_WEEK)
    //                                 ? fields[NFIELDS + DAY_OF_WEEK] : cal.getFirstDayOfWeek();
    //                 cal.setWeekDate(fields[NFIELDS + WEEK_YEAR], weekOfYear, dayOfWeek);
    //             }
    //             cal.complete();
    //         }

    //         return cal;
    //     }

    //     private void allocateFields() {
    //         if (fields is null) {
    //             fields = new int[NFIELDS * 2];
    //             nextStamp = MINIMUM_USER_STAMP;
    //             maxFieldIndex = -1;
    //         }
    //     }

    //     private void internalSet(int field, int value) {
    //         fields[field] = nextStamp++;
    //         if (nextStamp < 0) {
    //             throw new IllegalStateException("stamp counter overflow");
    //         }
    //         fields[NFIELDS + field] = value;
    //         if (field > maxFieldIndex && field < WEEK_YEAR) {
    //             maxFieldIndex = field;
    //         }
    //     }

    //     private bool isInstantSet() {
    //         return nextStamp == COMPUTED;
    //     }

    //     private bool isSet(int index) {
    //         return fields !is null && fields[index] > UNSET;
    //     }

    //     private bool isValidWeekParameter(int value) {
    //         return value > 0 && value <= 7;
    //     }
    // }

    /**
     * Constructs a Calendar with the default time zone
     * and the default {@link java.util.LocaleCategory#FORMAT FORMAT}
     * locale.
     * @see     TimeZone#getDefault
     */
    // protected this()
    // {
    //     this(TimeZone.getDefaultRef(), Locale.getDefault(LocaleCategory.FORMAT));
    //     sharedZone = true;
    // }

    // /**
    //  * Constructs a calendar with the specified time zone and locale.
    //  *
    //  * @param zone the time zone to use
    //  * @param aLocale the locale for the week data
    //  */
    // protected Calendar(TimeZone zone, Locale aLocale)
    // {
    //     fields = new int[FIELD_COUNT];
    //     isSet = new bool[FIELD_COUNT];
    //     stamp = new int[FIELD_COUNT];

    //     this.zone = zone;
    //     setWeekCountData(aLocale);
    // }

    /**
     * Gets a calendar using the default time zone and locale. The
     * <code>Calendar</code> returned is based on the current time
     * in the default time zone with the default
     * {@link LocaleCategory#FORMAT FORMAT} locale.
     * <p>
     * If the locale contains the time zone with "tz"
     * <a href="Locale.html#def_locale_extension">Unicode extension</a>,
     * that time zone is used instead.
     *
     * @return a Calendar.
     */
    static Calendar getInstance()
    {
        Locale aLocale = Locale.getDefault(LocaleCategory.FORMAT);
        return createCalendar(defaultTimeZone(aLocale), aLocale);
    }

    /**
     * Gets a calendar using the specified time zone and default locale.
     * The <code>Calendar</code> returned is based on the current time
     * in the given time zone with the default
     * {@link LocaleCategory#FORMAT FORMAT} locale.
     *
     * @param zone the time zone to use
     * @return a Calendar.
     */
    static Calendar getInstance(TimeZone zone)
    {
        return createCalendar(zone, Locale.getDefault(LocaleCategory.FORMAT));
    }

    /**
     * Gets a calendar using the default time zone and specified locale.
     * The <code>Calendar</code> returned is based on the current time
     * in the default time zone with the given locale.
     * <p>
     * If the locale contains the time zone with "tz"
     * <a href="Locale.html#def_locale_extension">Unicode extension</a>,
     * that time zone is used instead.
     *
     * @param aLocale the locale for the week data
     * @return a Calendar.
     */
    static Calendar getInstance(Locale aLocale)
    {
        return createCalendar(defaultTimeZone(aLocale), aLocale);
    }

    /**
     * Gets a calendar with the specified time zone and locale.
     * The <code>Calendar</code> returned is based on the current time
     * in the given time zone with the given locale.
     *
     * @param zone the time zone to use
     * @param aLocale the locale for the week data
     * @return a Calendar.
     */
    static Calendar getInstance(TimeZone zone,
                                       Locale aLocale)
    {
        return createCalendar(zone, aLocale);
    }

    private static TimeZone defaultTimeZone(Locale l) {
        import hunt.system.TimeZone;
        string tzId = getSystemTimeZoneId();
        version(Posix) {
            return cast(TimeZone)PosixTimeZone.getTimeZone(tzId);
        } else version(Windows) {
            return cast(TimeZone)WindowsTimeZone.getTimeZone(tzId);
        } else {
            return cast(TimeZone)LocalTime();
        }
        // TimeZone defaultTZ = TimeZone.getDefault();
        // TODO: Tasks pending completion -@zxp at 12/20/2018, 7:53:18 PM
        // 
        // return defaultTZ;
        // String shortTZID = l.getUnicodeLocaleType("tz");
        // return shortTZID !is null ?
        //     TimeZoneNameUtility.convertLDMLShortID(shortTZID)
        //         .map(TimeZone::getTimeZone)
        //         .orElse(defaultTZ) :
        //     defaultTZ;
    }

    private static Calendar createCalendar(TimeZone zone,
                                           Locale aLocale)
    {
        // CalendarProvider provider =
        //     LocaleProviderAdapter.getAdapter(CalendarProvider.class, aLocale)
        //                          .getCalendarProvider();
        // if (provider !is null) {
        //     try {
        //         return provider.getInstance(zone, aLocale);
        //     } catch (IllegalArgumentException iae) {
        //         // fall back to the default instantiation
        //     }
        // }

        // Calendar cal = new GregorianCalendar(zone, aLocale);
        // return cal;

        // if (aLocale.hasExtensions()) {
        //     String caltype = aLocale.getUnicodeLocaleType("ca");
        //     if (caltype !is null) {
        //         switch (caltype) {
        //         case "buddhist":
        //         cal = new BuddhistCalendar(zone, aLocale);
        //             break;
        //         case "japanese":
        //             cal = new JapaneseImperialCalendar(zone, aLocale);
        //             break;
        //         case "gregory":
        //             cal = new GregorianCalendar(zone, aLocale);
        //             break;
        //         }
        //     }
        // }
        // if (cal is null) {
        //     // If no known calendar type is explicitly specified,
        //     // perform the traditional way to create a Calendar:
        //     // create a BuddhistCalendar for th_TH locale,
        //     // a JapaneseImperialCalendar for ja_JP_JP locale, or
        //     // a GregorianCalendar for any other locales.
        //     // NOTE: The language, country and variant strings are interned.
        //     if (aLocale.getLanguage() == "th" && aLocale.getCountry() == "TH") {
        //         cal = new BuddhistCalendar(zone, aLocale);
        //     } else if (aLocale.getVariant() == "JP" && aLocale.getLanguage() == "ja"
        //                && aLocale.getCountry() == "JP") {
        //         cal = new JapaneseImperialCalendar(zone, aLocale);
        //     } else {
        //         cal = new GregorianCalendar(zone, aLocale);
        //     }
        // }
        // return cal;
        
        implementationMissing(false);
        return null;
    }

    // /**
    //  * Returns an array of all locales for which the <code>getInstance</code>
    //  * methods of this class can return localized instances.
    //  * The array returned must contain at least a <code>Locale</code>
    //  * instance equal to {@link java.util.Locale#US Locale.US}.
    //  *
    //  * @return An array of locales for which localized
    //  *         <code>Calendar</code> instances are available.
    //  */
    // static synchronized Locale[] getAvailableLocales()
    // {
    //     return DateFormat.getAvailableLocales();
    // }

    // /**
    //  * Converts the current calendar field values in {@link #fields fields[]}
    //  * to the millisecond time value
    //  * {@link #time}.
    //  *
    //  * @see #complete()
    //  * @see #computeFields()
    //  */
    // protected abstract void computeTime();

    // /**
    //  * Converts the current millisecond time value {@link #time}
    //  * to calendar field values in {@link #fields fields[]}.
    //  * This allows you to sync up the calendar field values with
    //  * a new time that is set for the calendar.  The time is <em>not</em>
    //  * recomputed first; to recompute the time, then the fields, call the
    //  * {@link #complete()} method.
    //  *
    //  * @see #computeTime()
    //  */
    // protected abstract void computeFields();

    // /**
    //  * Returns a <code>LocalDateTime</code> object representing this
    //  * <code>Calendar</code>'s time value (millisecond offset from the <a
    //  * href="#Epoch">Epoch</a>").
    //  *
    //  * @return a <code>LocalDateTime</code> representing the time value.
    //  * @see #setTime(LocalDateTime)
    //  * @see #getTimeInMillis()
    //  */
    // const LocalDateTime getTime() {
    //     return new LocalDateTime(getTimeInMillis());
    // }

    // /**
    //  * Sets this Calendar's time with the given <code>LocalDateTime</code>.
    //  * <p>
    //  * Note: Calling <code>setTime()</code> with
    //  * <code>LocalDateTime(Long.MAX_VALUE)</code> or <code>LocalDateTime(Long.MIN_VALUE)</code>
    //  * may yield incorrect field values from <code>get()</code>.
    //  *
    //  * @param date the given LocalDateTime.
    //  * @see #getTime()
    //  * @see #setTimeInMillis(long)
    //  */
    // const void setTime(LocalDateTime date) {
    //     setTimeInMillis(date.getTime());
    // }

    // /**
    //  * Returns this Calendar's time value in milliseconds.
    //  *
    //  * @return the current time as UTC milliseconds from the epoch.
    //  * @see #getTime()
    //  * @see #setTimeInMillis(long)
    //  */
    // long getTimeInMillis() {
    //     if (!isTimeSet) {
    //         updateTime();
    //     }
    //     return time;
    // }

    // /**
    //  * Sets this Calendar's current time from the given long value.
    //  *
    //  * @param millis the new time in UTC milliseconds from the epoch.
    //  * @see #setTime(LocalDateTime)
    //  * @see #getTimeInMillis()
    //  */
    // void setTimeInMillis(long millis) {
    //     // If we don't need to recalculate the calendar field values,
    //     // do nothing.
    //     if (time == millis && isTimeSet && areFieldsSet && areAllFieldsSet
    //         && (zone instanceof ZoneInfo) && !((ZoneInfo)zone).isDirty()) {
    //         return;
    //     }
    //     time = millis;
    //     isTimeSet = true;
    //     areFieldsSet = false;
    //     computeFields();
    //     areAllFieldsSet = areFieldsSet = true;
    // }

    // /**
    //  * Returns the value of the given calendar field. In lenient mode,
    //  * all calendar fields are normalized. In non-lenient mode, all
    //  * calendar fields are validated and this method throws an
    //  * exception if any calendar fields have out-of-range values. The
    //  * normalization and validation are handled by the
    //  * {@link #complete()} method, which process is calendar
    //  * system dependent.
    //  *
    //  * @param field the given calendar field.
    //  * @return the value for the given calendar field.
    //  * @throws ArrayIndexOutOfBoundsException if the specified field is out of range
    //  *             (<code>field &lt; 0 || field &gt;= FIELD_COUNT</code>).
    //  * @see #set(int,int)
    //  * @see #complete()
    //  */
    // int get(int field)
    // {
    //     complete();
    //     return internalGet(field);
    // }

    // /**
    //  * Returns the value of the given calendar field. This method does
    //  * not involve normalization or validation of the field value.
    //  *
    //  * @param field the given calendar field.
    //  * @return the value for the given calendar field.
    //  * @see #get(int)
    //  */
    // protected const int internalGet(int field)
    // {
    //     return fields[field];
    // }

    // /**
    //  * Sets the value of the given calendar field. This method does
    //  * not affect any setting state of the field in this
    //  * <code>Calendar</code> instance.
    //  *
    //  * @throws IndexOutOfBoundsException if the specified field is out of range
    //  *             (<code>field &lt; 0 || field &gt;= FIELD_COUNT</code>).
    //  * @see #areFieldsSet
    //  * @see #isTimeSet
    //  * @see #areAllFieldsSet
    //  * @see #set(int,int)
    //  */
    // const void internalSet(int field, int value)
    // {
    //     fields[field] = value;
    // }

    // /**
    //  * Sets the given calendar field to the given value. The value is not
    //  * interpreted by this method regardless of the leniency mode.
    //  *
    //  * @param field the given calendar field.
    //  * @param value the value to be set for the given calendar field.
    //  * @throws ArrayIndexOutOfBoundsException if the specified field is out of range
    //  *             (<code>field &lt; 0 || field &gt;= FIELD_COUNT</code>).
    //  * in non-lenient mode.
    //  * @see #set(int,int,int)
    //  * @see #set(int,int,int,int,int)
    //  * @see #set(int,int,int,int,int,int)
    //  * @see #get(int)
    //  */
    // void set(int field, int value)
    // {
    //     // If the fields are partially normalized, calculate all the
    //     // fields before changing any fields.
    //     if (areFieldsSet && !areAllFieldsSet) {
    //         computeFields();
    //     }
    //     internalSet(field, value);
    //     isTimeSet = false;
    //     areFieldsSet = false;
    //     isSet[field] = true;
    //     stamp[field] = nextStamp++;
    //     if (nextStamp == Integer.MAX_VALUE) {
    //         adjustStamp();
    //     }
    // }

    // /**
    //  * Sets the values for the calendar fields <code>YEAR</code>,
    //  * <code>MONTH</code>, and <code>DAY_OF_MONTH</code>.
    //  * Previous values of other calendar fields are retained.  If this is not desired,
    //  * call {@link #clear()} first.
    //  *
    //  * @param year the value used to set the <code>YEAR</code> calendar field.
    //  * @param month the value used to set the <code>MONTH</code> calendar field.
    //  * Month value is 0-based. e.g., 0 for January.
    //  * @param date the value used to set the <code>DAY_OF_MONTH</code> calendar field.
    //  * @see #set(int,int)
    //  * @see #set(int,int,int,int,int)
    //  * @see #set(int,int,int,int,int,int)
    //  */
    // const void set(int year, int month, int date)
    // {
    //     set(YEAR, year);
    //     set(MONTH, month);
    //     set(DATE, date);
    // }

    // /**
    //  * Sets the values for the calendar fields <code>YEAR</code>,
    //  * <code>MONTH</code>, <code>DAY_OF_MONTH</code>,
    //  * <code>HOUR_OF_DAY</code>, and <code>MINUTE</code>.
    //  * Previous values of other fields are retained.  If this is not desired,
    //  * call {@link #clear()} first.
    //  *
    //  * @param year the value used to set the <code>YEAR</code> calendar field.
    //  * @param month the value used to set the <code>MONTH</code> calendar field.
    //  * Month value is 0-based. e.g., 0 for January.
    //  * @param date the value used to set the <code>DAY_OF_MONTH</code> calendar field.
    //  * @param hourOfDay the value used to set the <code>HOUR_OF_DAY</code> calendar field.
    //  * @param minute the value used to set the <code>MINUTE</code> calendar field.
    //  * @see #set(int,int)
    //  * @see #set(int,int,int)
    //  * @see #set(int,int,int,int,int,int)
    //  */
    // const void set(int year, int month, int date, int hourOfDay, int minute)
    // {
    //     set(YEAR, year);
    //     set(MONTH, month);
    //     set(DATE, date);
    //     set(HOUR_OF_DAY, hourOfDay);
    //     set(MINUTE, minute);
    // }

    // /**
    //  * Sets the values for the fields <code>YEAR</code>, <code>MONTH</code>,
    //  * <code>DAY_OF_MONTH</code>, <code>HOUR_OF_DAY</code>, <code>MINUTE</code>, and
    //  * <code>SECOND</code>.
    //  * Previous values of other fields are retained.  If this is not desired,
    //  * call {@link #clear()} first.
    //  *
    //  * @param year the value used to set the <code>YEAR</code> calendar field.
    //  * @param month the value used to set the <code>MONTH</code> calendar field.
    //  * Month value is 0-based. e.g., 0 for January.
    //  * @param date the value used to set the <code>DAY_OF_MONTH</code> calendar field.
    //  * @param hourOfDay the value used to set the <code>HOUR_OF_DAY</code> calendar field.
    //  * @param minute the value used to set the <code>MINUTE</code> calendar field.
    //  * @param second the value used to set the <code>SECOND</code> calendar field.
    //  * @see #set(int,int)
    //  * @see #set(int,int,int)
    //  * @see #set(int,int,int,int,int)
    //  */
    // const void set(int year, int month, int date, int hourOfDay, int minute,
    //                       int second)
    // {
    //     set(YEAR, year);
    //     set(MONTH, month);
    //     set(DATE, date);
    //     set(HOUR_OF_DAY, hourOfDay);
    //     set(MINUTE, minute);
    //     set(SECOND, second);
    // }

    // /**
    //  * Sets all the calendar field values and the time value
    //  * (millisecond offset from the <a href="#Epoch">Epoch</a>) of
    //  * this <code>Calendar</code> undefined. This means that {@link
    //  * #isSet(int) isSet()} will return <code>false</code> for all the
    //  * calendar fields, and the date and time calculations will treat
    //  * the fields as if they had never been set. A
    //  * <code>Calendar</code> implementation class may use its specific
    //  * default field values for date/time calculations. For example,
    //  * <code>GregorianCalendar</code> uses 1970 if the
    //  * <code>YEAR</code> field value is undefined.
    //  *
    //  * @see #clear(int)
    //  */
    // const void clear()
    // {
    //     for (int i = 0; i < fields.length; ) {
    //         stamp[i] = fields[i] = 0; // UNSET == 0
    //         isSet[i++] = false;
    //     }
    //     areAllFieldsSet = areFieldsSet = false;
    //     isTimeSet = false;
    // }

    // /**
    //  * Sets the given calendar field value and the time value
    //  * (millisecond offset from the <a href="#Epoch">Epoch</a>) of
    //  * this <code>Calendar</code> undefined. This means that {@link
    //  * #isSet(int) isSet(field)} will return <code>false</code>, and
    //  * the date and time calculations will treat the field as if it
    //  * had never been set. A <code>Calendar</code> implementation
    //  * class may use the field's specific default value for date and
    //  * time calculations.
    //  *
    //  * <p>The {@link #HOUR_OF_DAY}, {@link #HOUR} and {@link #AM_PM}
    //  * fields are handled independently and the <a
    //  * href="#time_resolution">the resolution rule for the time of
    //  * day</a> is applied. Clearing one of the fields doesn't reset
    //  * the hour of day value of this <code>Calendar</code>. Use {@link
    //  * #set(int,int) set(Calendar.HOUR_OF_DAY, 0)} to reset the hour
    //  * value.
    //  *
    //  * @param field the calendar field to be cleared.
    //  * @see #clear()
    //  */
    // const void clear(int field)
    // {
    //     fields[field] = 0;
    //     stamp[field] = UNSET;
    //     isSet[field] = false;

    //     areAllFieldsSet = areFieldsSet = false;
    //     isTimeSet = false;
    // }

    // /**
    //  * Determines if the given calendar field has a value set,
    //  * including cases that the value has been set by internal fields
    //  * calculations triggered by a <code>get</code> method call.
    //  *
    //  * @param field the calendar field to test
    //  * @return <code>true</code> if the given calendar field has a value set;
    //  * <code>false</code> otherwise.
    //  */
    // const bool isSet(int field)
    // {
    //     return stamp[field] != UNSET;
    // }

    // /**
    //  * Returns the string representation of the calendar
    //  * <code>field</code> value in the given <code>style</code> and
    //  * <code>locale</code>.  If no string representation is
    //  * applicable, <code>null</code> is returned. This method calls
    //  * {@link Calendar#get(int) get(field)} to get the calendar
    //  * <code>field</code> value if the string representation is
    //  * applicable to the given calendar <code>field</code>.
    //  *
    //  * <p>For example, if this <code>Calendar</code> is a
    //  * <code>GregorianCalendar</code> and its date is 2005-01-01, then
    //  * the string representation of the {@link #MONTH} field would be
    //  * "January" in the long style in an English locale or "Jan" in
    //  * the short style. However, no string representation would be
    //  * available for the {@link #DAY_OF_MONTH} field, and this method
    //  * would return <code>null</code>.
    //  *
    //  * <p>The default implementation supports the calendar fields for
    //  * which a {@link DateFormatSymbols} has names in the given
    //  * <code>locale</code>.
    //  *
    //  * @param field
    //  *        the calendar field for which the string representation
    //  *        is returned
    //  * @param style
    //  *        the style applied to the string representation; one of {@link
    //  *        #SHORT_FORMAT} ({@link #SHORT}), {@link #SHORT_STANDALONE},
    //  *        {@link #LONG_FORMAT} ({@link #LONG}), {@link #LONG_STANDALONE},
    //  *        {@link #NARROW_FORMAT}, or {@link #NARROW_STANDALONE}.
    //  * @param locale
    //  *        the locale for the string representation
    //  *        (any calendar types specified by {@code locale} are ignored)
    //  * @return the string representation of the given
    //  *        {@code field} in the given {@code style}, or
    //  *        {@code null} if no string representation is
    //  *        applicable.
    //  * @exception IllegalArgumentException
    //  *        if {@code field} or {@code style} is invalid,
    //  *        or if this {@code Calendar} is non-lenient and any
    //  *        of the calendar fields have invalid values
    //  * @exception NullPointerException
    //  *        if {@code locale} is null
    //  * @since 1.6
    //  */
    // String getDisplayName(int field, int style, Locale locale) {
    //     if (!checkDisplayNameParams(field, style, SHORT, NARROW_FORMAT, locale,
    //                         ERA_MASK|MONTH_MASK|DAY_OF_WEEK_MASK|AM_PM_MASK)) {
    //         return null;
    //     }

    //     String calendarType = getCalendarType();
    //     int fieldValue = get(field);
    //     // the standalone/narrow styles and short era are supported only through
    //     // CalendarNameProviders.
    //     if (isStandaloneStyle(style) || isNarrowFormatStyle(style) ||
    //         field == ERA && (style & SHORT) == SHORT) {
    //         String val = CalendarDataUtility.retrieveFieldValueName(calendarType,
    //                                                                 field, fieldValue,
    //                                                                 style, locale);
    //         // Perform fallback here to follow the CLDR rules
    //         if (val is null) {
    //             if (isNarrowFormatStyle(style)) {
    //                 val = CalendarDataUtility.retrieveFieldValueName(calendarType,
    //                                                                  field, fieldValue,
    //                                                                  toStandaloneStyle(style),
    //                                                                  locale);
    //             } else if (isStandaloneStyle(style)) {
    //                 val = CalendarDataUtility.retrieveFieldValueName(calendarType,
    //                                                                  field, fieldValue,
    //                                                                  getBaseStyle(style),
    //                                                                  locale);
    //             }
    //         }
    //         return val;
    //     }

    //     DateFormatSymbols symbols = DateFormatSymbols.getInstance(locale);
    //     String[] strings = getFieldStrings(field, style, symbols);
    //     if (strings !is null) {
    //         if (fieldValue < strings.length) {
    //             return strings[fieldValue];
    //         }
    //     }
    //     return null;
    // }

    // /**
    //  * Returns a {@code Map} containing all names of the calendar
    //  * {@code field} in the given {@code style} and
    //  * {@code locale} and their corresponding field values. For
    //  * example, if this {@code Calendar} is a {@link
    //  * GregorianCalendar}, the returned map would contain "Jan" to
    //  * {@link #JANUARY}, "Feb" to {@link #FEBRUARY}, and so on, in the
    //  * {@linkplain #SHORT short} style in an English locale.
    //  *
    //  * <p>Narrow names may not be unique due to use of single characters,
    //  * such as "S" for Sunday and Saturday. In that case narrow names are not
    //  * included in the returned {@code Map}.
    //  *
    //  * <p>The values of other calendar fields may be taken into
    //  * account to determine a set of display names. For example, if
    //  * this {@code Calendar} is a lunisolar calendar system and
    //  * the year value given by the {@link #YEAR} field has a leap
    //  * month, this method would return month names containing the leap
    //  * month name, and month names are mapped to their values specific
    //  * for the year.
    //  *
    //  * <p>The default implementation supports display names contained in
    //  * a {@link DateFormatSymbols}. For example, if {@code field}
    //  * is {@link #MONTH} and {@code style} is {@link
    //  * #ALL_STYLES}, this method returns a {@code Map} containing
    //  * all strings returned by {@link DateFormatSymbols#getShortMonths()}
    //  * and {@link DateFormatSymbols#getMonths()}.
    //  *
    //  * @param field
    //  *        the calendar field for which the display names are returned
    //  * @param style
    //  *        the style applied to the string representation; one of {@link
    //  *        #SHORT_FORMAT} ({@link #SHORT}), {@link #SHORT_STANDALONE},
    //  *        {@link #LONG_FORMAT} ({@link #LONG}), {@link #LONG_STANDALONE},
    //  *        {@link #NARROW_FORMAT}, or {@link #NARROW_STANDALONE}
    //  * @param locale
    //  *        the locale for the display names
    //  * @return a {@code Map} containing all display names in
    //  *        {@code style} and {@code locale} and their
    //  *        field values, or {@code null} if no display names
    //  *        are defined for {@code field}
    //  * @exception IllegalArgumentException
    //  *        if {@code field} or {@code style} is invalid,
    //  *        or if this {@code Calendar} is non-lenient and any
    //  *        of the calendar fields have invalid values
    //  * @exception NullPointerException
    //  *        if {@code locale} is null
    //  * @since 1.6
    //  */
    // Map<String, Integer> getDisplayNames(int field, int style, Locale locale) {
    //     if (!checkDisplayNameParams(field, style, ALL_STYLES, NARROW_FORMAT, locale,
    //                                 ERA_MASK|MONTH_MASK|DAY_OF_WEEK_MASK|AM_PM_MASK)) {
    //         return null;
    //     }

    //     String calendarType = getCalendarType();
    //     if (style == ALL_STYLES || isStandaloneStyle(style) || isNarrowFormatStyle(style)) {
    //         Map<String, Integer> map;
    //         map = CalendarDataUtility.retrieveFieldValueNames(calendarType, field, style, locale);

    //         // Perform fallback here to follow the CLDR rules
    //         if (map is null) {
    //             if (isNarrowFormatStyle(style)) {
    //                 map = CalendarDataUtility.retrieveFieldValueNames(calendarType, field,
    //                                                                   toStandaloneStyle(style), locale);
    //             } else if (style != ALL_STYLES) {
    //                 map = CalendarDataUtility.retrieveFieldValueNames(calendarType, field,
    //                                                                   getBaseStyle(style), locale);
    //             }
    //         }
    //         return map;
    //     }

    //     // SHORT or LONG
    //     return getDisplayNamesImpl(field, style, locale);
    // }

    // private Map<String,Integer> getDisplayNamesImpl(int field, int style, Locale locale) {
    //     DateFormatSymbols symbols = DateFormatSymbols.getInstance(locale);
    //     String[] strings = getFieldStrings(field, style, symbols);
    //     if (strings !is null) {
    //         Map<String,Integer> names = new HashMap<>();
    //         for (int i = 0; i < strings.length; i++) {
    //             if (strings[i].length() == 0) {
    //                 continue;
    //             }
    //             names.put(strings[i], i);
    //         }
    //         return names;
    //     }
    //     return null;
    // }

    // bool checkDisplayNameParams(int field, int style, int minStyle, int maxStyle,
    //                                Locale locale, int fieldMask) {
    //     int baseStyle = getBaseStyle(style); // Ignore the standalone mask
    //     if (field < 0 || field >= fields.length ||
    //         baseStyle < minStyle || baseStyle > maxStyle || baseStyle == 3) {
    //         throw new IllegalArgumentException();
    //     }
    //     if (locale is null) {
    //         throw new NullPointerException();
    //     }
    //     return isFieldSet(fieldMask, field);
    // }

    // private String[] getFieldStrings(int field, int style, DateFormatSymbols symbols) {
    //     int baseStyle = getBaseStyle(style); // ignore the standalone mask

    //     // DateFormatSymbols doesn't support any narrow names.
    //     if (baseStyle == NARROW_FORMAT) {
    //         return null;
    //     }

    //     String[] strings = null;
    //     switch (field) {
    //     case ERA:
    //         strings = symbols.getEras();
    //         break;

    //     case MONTH:
    //         strings = (baseStyle == LONG) ? symbols.getMonths() : symbols.getShortMonths();
    //         break;

    //     case DAY_OF_WEEK:
    //         strings = (baseStyle == LONG) ? symbols.getWeekdays() : symbols.getShortWeekdays();
    //         break;

    //     case AM_PM:
    //         strings = symbols.getAmPmStrings();
    //         break;
    //     }
    //     return strings;
    // }

    // /**
    //  * Fills in any unset fields in the calendar fields. First, the {@link
    //  * #computeTime()} method is called if the time value (millisecond offset
    //  * from the <a href="#Epoch">Epoch</a>) has not been calculated from
    //  * calendar field values. Then, the {@link #computeFields()} method is
    //  * called to calculate all calendar field values.
    //  */
    // protected void complete()
    // {
    //     if (!isTimeSet) {
    //         updateTime();
    //     }
    //     if (!areFieldsSet || !areAllFieldsSet) {
    //         computeFields(); // fills in unset fields
    //         areAllFieldsSet = areFieldsSet = true;
    //     }
    // }

    // /**
    //  * Returns whether the value of the specified calendar field has been set
    //  * externally by calling one of the setter methods rather than by the
    //  * internal time calculation.
    //  *
    //  * @return <code>true</code> if the field has been set externally,
    //  * <code>false</code> otherwise.
    //  * @exception IndexOutOfBoundsException if the specified
    //  *                <code>field</code> is out of range
    //  *               (<code>field &lt; 0 || field &gt;= FIELD_COUNT</code>).
    //  * @see #selectFields()
    //  * @see #setFieldsComputed(int)
    //  */
    // const bool isExternallySet(int field) {
    //     return stamp[field] >= MINIMUM_USER_STAMP;
    // }

    // /**
    //  * Returns a field mask (bit mask) indicating all calendar fields that
    //  * have the state of externally or internally set.
    //  *
    //  * @return a bit mask indicating set state fields
    //  */
    // const int getSetStateFields() {
    //     int mask = 0;
    //     for (int i = 0; i < fields.length; i++) {
    //         if (stamp[i] != UNSET) {
    //             mask |= 1 << i;
    //         }
    //     }
    //     return mask;
    // }

    // /**
    //  * Sets the state of the specified calendar fields to
    //  * <em>computed</em>. This state means that the specified calendar fields
    //  * have valid values that have been set by internal time calculation
    //  * rather than by calling one of the setter methods.
    //  *
    //  * @param fieldMask the field to be marked as computed.
    //  * @exception IndexOutOfBoundsException if the specified
    //  *                <code>field</code> is out of range
    //  *               (<code>field &lt; 0 || field &gt;= FIELD_COUNT</code>).
    //  * @see #isExternallySet(int)
    //  * @see #selectFields()
    //  */
    // const void setFieldsComputed(int fieldMask) {
    //     if (fieldMask == ALL_FIELDS) {
    //         for (int i = 0; i < fields.length; i++) {
    //             stamp[i] = COMPUTED;
    //             isSet[i] = true;
    //         }
    //         areFieldsSet = areAllFieldsSet = true;
    //     } else {
    //         for (int i = 0; i < fields.length; i++) {
    //             if ((fieldMask & 1) == 1) {
    //                 stamp[i] = COMPUTED;
    //                 isSet[i] = true;
    //             } else {
    //                 if (areAllFieldsSet && !isSet[i]) {
    //                     areAllFieldsSet = false;
    //                 }
    //             }
    //             fieldMask >>>= 1;
    //         }
    //     }
    // }

    // /**
    //  * Sets the state of the calendar fields that are <em>not</em> specified
    //  * by <code>fieldMask</code> to <em>unset</em>. If <code>fieldMask</code>
    //  * specifies all the calendar fields, then the state of this
    //  * <code>Calendar</code> becomes that all the calendar fields are in sync
    //  * with the time value (millisecond offset from the Epoch).
    //  *
    //  * @param fieldMask the field mask indicating which calendar fields are in
    //  * sync with the time value.
    //  * @exception IndexOutOfBoundsException if the specified
    //  *                <code>field</code> is out of range
    //  *               (<code>field &lt; 0 || field &gt;= FIELD_COUNT</code>).
    //  * @see #isExternallySet(int)
    //  * @see #selectFields()
    //  */
    // const void setFieldsNormalized(int fieldMask) {
    //     if (fieldMask != ALL_FIELDS) {
    //         for (int i = 0; i < fields.length; i++) {
    //             if ((fieldMask & 1) == 0) {
    //                 stamp[i] = fields[i] = 0; // UNSET == 0
    //                 isSet[i] = false;
    //             }
    //             fieldMask >>= 1;
    //         }
    //     }

    //     // Some or all of the fields are in sync with the
    //     // milliseconds, but the stamp values are not normalized yet.
    //     areFieldsSet = true;
    //     areAllFieldsSet = false;
    // }

    // /**
    //  * Returns whether the calendar fields are partially in sync with the time
    //  * value or fully in sync but not stamp values are not normalized yet.
    //  */
    // const bool isPartiallyNormalized() {
    //     return areFieldsSet && !areAllFieldsSet;
    // }

    // /**
    //  * Returns whether the calendar fields are fully in sync with the time
    //  * value.
    //  */
    // const bool isFullyNormalized() {
    //     return areFieldsSet && areAllFieldsSet;
    // }

    // /**
    //  * Marks this Calendar as not sync'd.
    //  */
    // const void setUnnormalized() {
    //     areFieldsSet = areAllFieldsSet = false;
    // }

    // /**
    //  * Returns whether the specified <code>field</code> is on in the
    //  * <code>fieldMask</code>.
    //  */
    // static bool isFieldSet(int fieldMask, int field) {
    //     return (fieldMask & (1 << field)) != 0;
    // }

    // /**
    //  * Returns a field mask indicating which calendar field values
    //  * to be used to calculate the time value. The calendar fields are
    //  * returned as a bit mask, each bit of which corresponds to a field, i.e.,
    //  * the mask value of <code>field</code> is <code>(1 &lt;&lt;
    //  * field)</code>. For example, 0x26 represents the <code>YEAR</code>,
    //  * <code>MONTH</code>, and <code>DAY_OF_MONTH</code> fields (i.e., 0x26 is
    //  * equal to
    //  * <code>(1&lt;&lt;YEAR)|(1&lt;&lt;MONTH)|(1&lt;&lt;DAY_OF_MONTH))</code>.
    //  *
    //  * <p>This method supports the calendar fields resolution as described in
    //  * the class description. If the bit mask for a given field is on and its
    //  * field has not been set (i.e., <code>isSet(field)</code> is
    //  * <code>false</code>), then the default value of the field has to be
    //  * used, which case means that the field has been selected because the
    //  * selected combination involves the field.
    //  *
    //  * @return a bit mask of selected fields
    //  * @see #isExternallySet(int)
    //  */
    // const int selectFields() {
    //     // This implementation has been taken from the GregorianCalendar class.

    //     // The YEAR field must always be used regardless of its SET
    //     // state because YEAR is a mandatory field to determine the date
    //     // and the default value (EPOCH_YEAR) may change through the
    //     // normalization process.
    //     int fieldMask = YEAR_MASK;

    //     if (stamp[ERA] != UNSET) {
    //         fieldMask |= ERA_MASK;
    //     }
    //     // Find the most recent group of fields specifying the day within
    //     // the year.  These may be any of the following combinations:
    //     //   MONTH + DAY_OF_MONTH
    //     //   MONTH + WEEK_OF_MONTH + DAY_OF_WEEK
    //     //   MONTH + DAY_OF_WEEK_IN_MONTH + DAY_OF_WEEK
    //     //   DAY_OF_YEAR
    //     //   WEEK_OF_YEAR + DAY_OF_WEEK
    //     // We look for the most recent of the fields in each group to determine
    //     // the age of the group.  For groups involving a week-related field such
    //     // as WEEK_OF_MONTH, DAY_OF_WEEK_IN_MONTH, or WEEK_OF_YEAR, both the
    //     // week-related field and the DAY_OF_WEEK must be set for the group as a
    //     // whole to be considered.  (See bug 4153860 - liu 7/24/98.)
    //     int dowStamp = stamp[DAY_OF_WEEK];
    //     int monthStamp = stamp[MONTH];
    //     int domStamp = stamp[DAY_OF_MONTH];
    //     int womStamp = aggregateStamp(stamp[WEEK_OF_MONTH], dowStamp);
    //     int dowimStamp = aggregateStamp(stamp[DAY_OF_WEEK_IN_MONTH], dowStamp);
    //     int doyStamp = stamp[DAY_OF_YEAR];
    //     int woyStamp = aggregateStamp(stamp[WEEK_OF_YEAR], dowStamp);

    //     int bestStamp = domStamp;
    //     if (womStamp > bestStamp) {
    //         bestStamp = womStamp;
    //     }
    //     if (dowimStamp > bestStamp) {
    //         bestStamp = dowimStamp;
    //     }
    //     if (doyStamp > bestStamp) {
    //         bestStamp = doyStamp;
    //     }
    //     if (woyStamp > bestStamp) {
    //         bestStamp = woyStamp;
    //     }

    //     /* No complete combination exists.  Look for WEEK_OF_MONTH,
    //      * DAY_OF_WEEK_IN_MONTH, or WEEK_OF_YEAR alone.  Treat DAY_OF_WEEK alone
    //      * as DAY_OF_WEEK_IN_MONTH.
    //      */
    //     if (bestStamp == UNSET) {
    //         womStamp = stamp[WEEK_OF_MONTH];
    //         dowimStamp = Math.max(stamp[DAY_OF_WEEK_IN_MONTH], dowStamp);
    //         woyStamp = stamp[WEEK_OF_YEAR];
    //         bestStamp = Math.max(Math.max(womStamp, dowimStamp), woyStamp);

    //         /* Treat MONTH alone or no fields at all as DAY_OF_MONTH.  This may
    //          * result in bestStamp = domStamp = UNSET if no fields are set,
    //          * which indicates DAY_OF_MONTH.
    //          */
    //         if (bestStamp == UNSET) {
    //             bestStamp = domStamp = monthStamp;
    //         }
    //     }

    //     if (bestStamp == domStamp ||
    //        (bestStamp == womStamp && stamp[WEEK_OF_MONTH] >= stamp[WEEK_OF_YEAR]) ||
    //        (bestStamp == dowimStamp && stamp[DAY_OF_WEEK_IN_MONTH] >= stamp[WEEK_OF_YEAR])) {
    //         fieldMask |= MONTH_MASK;
    //         if (bestStamp == domStamp) {
    //             fieldMask |= DAY_OF_MONTH_MASK;
    //         } else {
    //             assert (bestStamp == womStamp || bestStamp == dowimStamp);
    //             if (dowStamp != UNSET) {
    //                 fieldMask |= DAY_OF_WEEK_MASK;
    //             }
    //             if (womStamp == dowimStamp) {
    //                 // When they are equal, give the priority to
    //                 // WEEK_OF_MONTH for compatibility.
    //                 if (stamp[WEEK_OF_MONTH] >= stamp[DAY_OF_WEEK_IN_MONTH]) {
    //                     fieldMask |= WEEK_OF_MONTH_MASK;
    //                 } else {
    //                     fieldMask |= DAY_OF_WEEK_IN_MONTH_MASK;
    //                 }
    //             } else {
    //                 if (bestStamp == womStamp) {
    //                     fieldMask |= WEEK_OF_MONTH_MASK;
    //                 } else {
    //                     assert (bestStamp == dowimStamp);
    //                     if (stamp[DAY_OF_WEEK_IN_MONTH] != UNSET) {
    //                         fieldMask |= DAY_OF_WEEK_IN_MONTH_MASK;
    //                     }
    //                 }
    //             }
    //         }
    //     } else {
    //         assert (bestStamp == doyStamp || bestStamp == woyStamp ||
    //                 bestStamp == UNSET);
    //         if (bestStamp == doyStamp) {
    //             fieldMask |= DAY_OF_YEAR_MASK;
    //         } else {
    //             assert (bestStamp == woyStamp);
    //             if (dowStamp != UNSET) {
    //                 fieldMask |= DAY_OF_WEEK_MASK;
    //             }
    //             fieldMask |= WEEK_OF_YEAR_MASK;
    //         }
    //     }

    //     // Find the best set of fields specifying the time of day.  There
    //     // are only two possibilities here; the HOUR_OF_DAY or the
    //     // AM_PM and the HOUR.
    //     int hourOfDayStamp = stamp[HOUR_OF_DAY];
    //     int hourStamp = aggregateStamp(stamp[HOUR], stamp[AM_PM]);
    //     bestStamp = (hourStamp > hourOfDayStamp) ? hourStamp : hourOfDayStamp;

    //     // if bestStamp is still UNSET, then take HOUR or AM_PM. (See 4846659)
    //     if (bestStamp == UNSET) {
    //         bestStamp = Math.max(stamp[HOUR], stamp[AM_PM]);
    //     }

    //     // Hours
    //     if (bestStamp != UNSET) {
    //         if (bestStamp == hourOfDayStamp) {
    //             fieldMask |= HOUR_OF_DAY_MASK;
    //         } else {
    //             fieldMask |= HOUR_MASK;
    //             if (stamp[AM_PM] != UNSET) {
    //                 fieldMask |= AM_PM_MASK;
    //             }
    //         }
    //     }
    //     if (stamp[MINUTE] != UNSET) {
    //         fieldMask |= MINUTE_MASK;
    //     }
    //     if (stamp[SECOND] != UNSET) {
    //         fieldMask |= SECOND_MASK;
    //     }
    //     if (stamp[MILLISECOND] != UNSET) {
    //         fieldMask |= MILLISECOND_MASK;
    //     }
    //     if (stamp[ZONE_OFFSET] >= MINIMUM_USER_STAMP) {
    //             fieldMask |= ZONE_OFFSET_MASK;
    //     }
    //     if (stamp[DST_OFFSET] >= MINIMUM_USER_STAMP) {
    //         fieldMask |= DST_OFFSET_MASK;
    //     }

    //     return fieldMask;
    // }

    // int getBaseStyle(int style) {
    //     return style & ~STANDALONE_MASK;
    // }

    // private int toStandaloneStyle(int style) {
    //     return style | STANDALONE_MASK;
    // }

    // private bool isStandaloneStyle(int style) {
    //     return (style & STANDALONE_MASK) != 0;
    // }

    // private bool isNarrowStyle(int style) {
    //     return style == NARROW_FORMAT || style == NARROW_STANDALONE;
    // }

    // private bool isNarrowFormatStyle(int style) {
    //     return style == NARROW_FORMAT;
    // }

    // /**
    //  * Returns the pseudo-time-stamp for two fields, given their
    //  * individual pseudo-time-stamps.  If either of the fields
    //  * is unset, then the aggregate is unset.  Otherwise, the
    //  * aggregate is the later of the two stamps.
    //  */
    // private static int aggregateStamp(int stamp_a, int stamp_b) {
    //     if (stamp_a == UNSET || stamp_b == UNSET) {
    //         return UNSET;
    //     }
    //     return (stamp_a > stamp_b) ? stamp_a : stamp_b;
    // }

    // /**
    //  * Returns an unmodifiable {@code Set} containing all calendar types
    //  * supported by {@code Calendar} in the runtime environment. The available
    //  * calendar types can be used for the <a
    //  * href="Locale.html#def_locale_extension">Unicode locale extensions</a>.
    //  * The {@code Set} returned contains at least {@code "gregory"}. The
    //  * calendar types don't include aliases, such as {@code "gregorian"} for
    //  * {@code "gregory"}.
    //  *
    //  * @return an unmodifiable {@code Set} containing all available calendar types
    //  * @since 1.8
    //  * @see #getCalendarType()
    //  * @see Calendar.Builder#setCalendarType(String)
    //  * @see Locale#getUnicodeLocaleType(String)
    //  */
    // static Set<String> getAvailableCalendarTypes() {
    //     return AvailableCalendarTypes.SET;
    // }

    // private static class AvailableCalendarTypes {
    //     private enum Set<String> SET;
    //     static {
    //         Set<String> set = new HashSet<>(3);
    //         set.add("gregory");
    //         set.add("buddhist");
    //         set.add("japanese");
    //         SET = Collections.unmodifiableSet(set);
    //     }
    //     private AvailableCalendarTypes() {
    //     }
    // }

    // /**
    //  * Returns the calendar type of this {@code Calendar}. Calendar types are
    //  * defined by the <em>Unicode Locale Data Markup Language (LDML)</em>
    //  * specification.
    //  *
    //  * <p>The default implementation of this method returns the class name of
    //  * this {@code Calendar} instance. Any subclasses that implement
    //  * LDML-defined calendar systems should override this method to return
    //  * appropriate calendar types.
    //  *
    //  * @return the LDML-defined calendar type or the class name of this
    //  *         {@code Calendar} instance
    //  * @since 1.8
    //  * @see <a href="Locale.html#def_extensions">Locale extensions</a>
    //  * @see Locale.Builder#setLocale(Locale)
    //  * @see Locale.Builder#setUnicodeLocaleKeyword(String, String)
    //  */
    // String getCalendarType() {
    //     return this.getClass().getName();
    // }

    // /**
    //  * Compares this <code>Calendar</code> to the specified
    //  * <code>Object</code>.  The result is <code>true</code> if and only if
    //  * the argument is a <code>Calendar</code> object of the same calendar
    //  * system that represents the same time value (millisecond offset from the
    //  * <a href="#Epoch">Epoch</a>) under the same
    //  * <code>Calendar</code> parameters as this object.
    //  *
    //  * <p>The <code>Calendar</code> parameters are the values represented
    //  * by the <code>isLenient</code>, <code>getFirstDayOfWeek</code>,
    //  * <code>getMinimalDaysInFirstWeek</code> and <code>getTimeZone</code>
    //  * methods. If there is any difference in those parameters
    //  * between the two <code>Calendar</code>s, this method returns
    //  * <code>false</code>.
    //  *
    //  * <p>Use the {@link #compareTo(Calendar) compareTo} method to
    //  * compare only the time values.
    //  *
    //  * @param obj the object to compare with.
    //  * @return <code>true</code> if this object is equal to <code>obj</code>;
    //  * <code>false</code> otherwise.
    //  */
    // //@SuppressWarnings("EqualsWhichDoesntCheckParameterClass")
    // @Override
    // bool equals(Object obj) {
    //     if (this is obj) {
    //         return true;
    //     }
    //     try {
    //         Calendar that = (Calendar)obj;
    //         return compareTo(getMillisOf(that)) == 0 &&
    //             lenient == that.lenient &&
    //             firstDayOfWeek == that.firstDayOfWeek &&
    //             minimalDaysInFirstWeek == that.minimalDaysInFirstWeek &&
    //             zone.equals(that.zone);
    //     } catch (Exception e) {
    //         // Note: GregorianCalendar.computeTime throws
    //         // IllegalArgumentException if the ERA value is invalid
    //         // even it's in lenient mode.
    //     }
    //     return false;
    // }

    // /**
    //  * Returns a hash code for this calendar.
    //  *
    //  * @return a hash code value for this object.
    //  * @since 1.2
    //  */
    // @Override
    // int hashCode() {
    //     // 'otheritems' represents the hash code for the previous versions.
    //     int otheritems = (lenient ? 1 : 0)
    //         | (firstDayOfWeek << 1)
    //         | (minimalDaysInFirstWeek << 4)
    //         | (zone.hashCode() << 7);
    //     long t = getMillisOf(this);
    //     return (int) t ^ (int)(t >> 32) ^ otheritems;
    // }

    // /**
    //  * Returns whether this <code>Calendar</code> represents a time
    //  * before the time represented by the specified
    //  * <code>Object</code>. This method is equivalent to:
    //  * <pre>{@code
    //  *         compareTo(when) < 0
    //  * }</pre>
    //  * if and only if <code>when</code> is a <code>Calendar</code>
    //  * instance. Otherwise, the method returns <code>false</code>.
    //  *
    //  * @param when the <code>Object</code> to be compared
    //  * @return <code>true</code> if the time of this
    //  * <code>Calendar</code> is before the time represented by
    //  * <code>when</code>; <code>false</code> otherwise.
    //  * @see     #compareTo(Calendar)
    //  */
    // bool before(Object when) {
    //     return when instanceof Calendar
    //         && compareTo((Calendar)when) < 0;
    // }

    // /**
    //  * Returns whether this <code>Calendar</code> represents a time
    //  * after the time represented by the specified
    //  * <code>Object</code>. This method is equivalent to:
    //  * <pre>{@code
    //  *         compareTo(when) > 0
    //  * }</pre>
    //  * if and only if <code>when</code> is a <code>Calendar</code>
    //  * instance. Otherwise, the method returns <code>false</code>.
    //  *
    //  * @param when the <code>Object</code> to be compared
    //  * @return <code>true</code> if the time of this <code>Calendar</code> is
    //  * after the time represented by <code>when</code>; <code>false</code>
    //  * otherwise.
    //  * @see     #compareTo(Calendar)
    //  */
    // bool after(Object when) {
    //     return when instanceof Calendar
    //         && compareTo((Calendar)when) > 0;
    // }

    // /**
    //  * Compares the time values (millisecond offsets from the <a
    //  * href="#Epoch">Epoch</a>) represented by two
    //  * <code>Calendar</code> objects.
    //  *
    //  * @param anotherCalendar the <code>Calendar</code> to be compared.
    //  * @return the value <code>0</code> if the time represented by the argument
    //  * is equal to the time represented by this <code>Calendar</code>; a value
    //  * less than <code>0</code> if the time of this <code>Calendar</code> is
    //  * before the time represented by the argument; and a value greater than
    //  * <code>0</code> if the time of this <code>Calendar</code> is after the
    //  * time represented by the argument.
    //  * @exception NullPointerException if the specified <code>Calendar</code> is
    //  *            <code>null</code>.
    //  * @exception IllegalArgumentException if the time value of the
    //  * specified <code>Calendar</code> object can't be obtained due to
    //  * any invalid calendar values.
    //  * @since   1.5
    //  */
    // @Override
    // int compareTo(Calendar anotherCalendar) {
    //     return compareTo(getMillisOf(anotherCalendar));
    // }

    // /**
    //  * Adds or subtracts the specified amount of time to the given calendar field,
    //  * based on the calendar's rules. For example, to subtract 5 days from
    //  * the current time of the calendar, you can achieve it by calling:
    //  * <p><code>add(Calendar.DAY_OF_MONTH, -5)</code>.
    //  *
    //  * @param field the calendar field.
    //  * @param amount the amount of date or time to be added to the field.
    //  * @see #roll(int,int)
    //  * @see #set(int,int)
    //  */
    // abstract void add(int field, int amount);

    // /**
    //  * Adds or subtracts (up/down) a single unit of time on the given time
    //  * field without changing larger fields. For example, to roll the current
    //  * date up by one day, you can achieve it by calling:
    //  * <p>roll(Calendar.DATE, true).
    //  * When rolling on the year or Calendar.YEAR field, it will roll the year
    //  * value in the range between 1 and the value returned by calling
    //  * <code>getMaximum(Calendar.YEAR)</code>.
    //  * When rolling on the month or Calendar.MONTH field, other fields like
    //  * date might conflict and, need to be changed. For instance,
    //  * rolling the month on the date 01/31/96 will result in 02/29/96.
    //  * When rolling on the hour-in-day or Calendar.HOUR_OF_DAY field, it will
    //  * roll the hour value in the range between 0 and 23, which is zero-based.
    //  *
    //  * @param field the time field.
    //  * @param up indicates if the value of the specified time field is to be
    //  * rolled up or rolled down. Use true if rolling up, false otherwise.
    //  * @see Calendar#add(int,int)
    //  * @see Calendar#set(int,int)
    //  */
    // abstract void roll(int field, bool up);

    // /**
    //  * Adds the specified (signed) amount to the specified calendar field
    //  * without changing larger fields.  A negative amount means to roll
    //  * down.
    //  *
    //  * <p>NOTE:  This default implementation on <code>Calendar</code> just repeatedly calls the
    //  * version of {@link #roll(int,bool) roll()} that rolls by one unit.  This may not
    //  * always do the right thing.  For example, if the <code>DAY_OF_MONTH</code> field is 31,
    //  * rolling through February will leave it set to 28.  The <code>GregorianCalendar</code>
    //  * version of this function takes care of this problem.  Other subclasses
    //  * should also provide overrides of this function that do the right thing.
    //  *
    //  * @param field the calendar field.
    //  * @param amount the signed amount to add to the calendar <code>field</code>.
    //  * @since 1.2
    //  * @see #roll(int,bool)
    //  * @see #add(int,int)
    //  * @see #set(int,int)
    //  */
    // void roll(int field, int amount)
    // {
    //     while (amount > 0) {
    //         roll(field, true);
    //         amount--;
    //     }
    //     while (amount < 0) {
    //         roll(field, false);
    //         amount++;
    //     }
    // }

    // /**
    //  * Sets the time zone with the given time zone value.
    //  *
    //  * @param value the given time zone.
    //  */
    // void setTimeZone(TimeZone value)
    // {
    //     zone = value;
    //     sharedZone = false;
    //     /* Recompute the fields from the time using the new zone.  This also
    //      * works if isTimeSet is false (after a call to set()).  In that case
    //      * the time will be computed from the fields using the new zone, then
    //      * the fields will get recomputed from that.  Consider the sequence of
    //      * calls: cal.setTimeZone(EST); cal.set(HOUR, 1); cal.setTimeZone(PST).
    //      * Is cal set to 1 o'clock EST or 1 o'clock PST?  Answer: PST.  More
    //      * generally, a call to setTimeZone() affects calls to set() BEFORE AND
    //      * AFTER it up to the next call to complete().
    //      */
    //     areAllFieldsSet = areFieldsSet = false;
    // }

    // /**
    //  * Gets the time zone.
    //  *
    //  * @return the time zone object associated with this calendar.
    //  */
    // TimeZone getTimeZone()
    // {
    //     // If the TimeZone object is shared by other Calendar instances, then
    //     // create a clone.
    //     if (sharedZone) {
    //         zone = (TimeZone) zone.clone();
    //         sharedZone = false;
    //     }
    //     return zone;
    // }

    // /**
    //  * Returns the time zone (without cloning).
    //  */
    // TimeZone getZone() {
    //     return zone;
    // }

    // /**
    //  * Sets the sharedZone flag to <code>shared</code>.
    //  */
    // void setZoneShared(bool shared) {
    //     sharedZone = shared;
    // }

    // /**
    //  * Specifies whether or not date/time interpretation is to be lenient.  With
    //  * lenient interpretation, a date such as "February 942, 1996" will be
    //  * treated as being equivalent to the 941st day after February 1, 1996.
    //  * With strict (non-lenient) interpretation, such dates will cause an exception to be
    //  * thrown. The default is lenient.
    //  *
    //  * @param lenient <code>true</code> if the lenient mode is to be turned
    //  * on; <code>false</code> if it is to be turned off.
    //  * @see #isLenient()
    //  * @see java.text.DateFormat#setLenient
    //  */
    // void setLenient(bool lenient)
    // {
    //     this.lenient = lenient;
    // }

    // /**
    //  * Tells whether date/time interpretation is to be lenient.
    //  *
    //  * @return <code>true</code> if the interpretation mode of this calendar is lenient;
    //  * <code>false</code> otherwise.
    //  * @see #setLenient(bool)
    //  */
    // bool isLenient()
    // {
    //     return lenient;
    // }

    // /**
    //  * Sets what the first day of the week is; e.g., <code>SUNDAY</code> in the U.S.,
    //  * <code>MONDAY</code> in France.
    //  *
    //  * @param value the given first day of the week.
    //  * @see #getFirstDayOfWeek()
    //  * @see #getMinimalDaysInFirstWeek()
    //  */
    // void setFirstDayOfWeek(int value)
    // {
    //     if (firstDayOfWeek == value) {
    //         return;
    //     }
    //     firstDayOfWeek = value;
    //     invalidateWeekFields();
    // }

    // /**
    //  * Gets what the first day of the week is; e.g., <code>SUNDAY</code> in the U.S.,
    //  * <code>MONDAY</code> in France.
    //  *
    //  * @return the first day of the week.
    //  * @see #setFirstDayOfWeek(int)
    //  * @see #getMinimalDaysInFirstWeek()
    //  */
    // int getFirstDayOfWeek()
    // {
    //     return firstDayOfWeek;
    // }

    // /**
    //  * Sets what the minimal days required in the first week of the year are;
    //  * For example, if the first week is defined as one that contains the first
    //  * day of the first month of a year, call this method with value 1. If it
    //  * must be a full week, use value 7.
    //  *
    //  * @param value the given minimal days required in the first week
    //  * of the year.
    //  * @see #getMinimalDaysInFirstWeek()
    //  */
    // void setMinimalDaysInFirstWeek(int value)
    // {
    //     if (minimalDaysInFirstWeek == value) {
    //         return;
    //     }
    //     minimalDaysInFirstWeek = value;
    //     invalidateWeekFields();
    // }

    // /**
    //  * Gets what the minimal days required in the first week of the year are;
    //  * e.g., if the first week is defined as one that contains the first day
    //  * of the first month of a year, this method returns 1. If
    //  * the minimal days required must be a full week, this method
    //  * returns 7.
    //  *
    //  * @return the minimal days required in the first week of the year.
    //  * @see #setMinimalDaysInFirstWeek(int)
    //  */
    // int getMinimalDaysInFirstWeek()
    // {
    //     return minimalDaysInFirstWeek;
    // }

    // /**
    //  * Returns whether this {@code Calendar} supports week dates.
    //  *
    //  * <p>The default implementation of this method returns {@code false}.
    //  *
    //  * @return {@code true} if this {@code Calendar} supports week dates;
    //  *         {@code false} otherwise.
    //  * @see #getWeekYear()
    //  * @see #setWeekDate(int,int,int)
    //  * @see #getWeeksInWeekYear()
    //  * @since 1.7
    //  */
    // bool isWeekDateSupported() {
    //     return false;
    // }

    // /**
    //  * Returns the week year represented by this {@code Calendar}. The
    //  * week year is in sync with the week cycle. The {@linkplain
    //  * #getFirstDayOfWeek() first day of the first week} is the first
    //  * day of the week year.
    //  *
    //  * <p>The default implementation of this method throws an
    //  * {@link UnsupportedOperationException}.
    //  *
    //  * @return the week year of this {@code Calendar}
    //  * @exception UnsupportedOperationException
    //  *            if any week year numbering isn't supported
    //  *            in this {@code Calendar}.
    //  * @see #isWeekDateSupported()
    //  * @see #getFirstDayOfWeek()
    //  * @see #getMinimalDaysInFirstWeek()
    //  * @since 1.7
    //  */
    // int getWeekYear() {
    //     throw new UnsupportedOperationException();
    // }

    // /**
    //  * Sets the date of this {@code Calendar} with the given date
    //  * specifiers - week year, week of year, and day of week.
    //  *
    //  * <p>Unlike the {@code set} method, all of the calendar fields
    //  * and {@code time} values are calculated upon return.
    //  *
    //  * <p>If {@code weekOfYear} is out of the valid week-of-year range
    //  * in {@code weekYear}, the {@code weekYear} and {@code
    //  * weekOfYear} values are adjusted in lenient mode, or an {@code
    //  * IllegalArgumentException} is thrown in non-lenient mode.
    //  *
    //  * <p>The default implementation of this method throws an
    //  * {@code UnsupportedOperationException}.
    //  *
    //  * @param weekYear   the week year
    //  * @param weekOfYear the week number based on {@code weekYear}
    //  * @param dayOfWeek  the day of week value: one of the constants
    //  *                   for the {@link #DAY_OF_WEEK} field: {@link
    //  *                   #SUNDAY}, ..., {@link #SATURDAY}.
    //  * @exception IllegalArgumentException
    //  *            if any of the given date specifiers is invalid
    //  *            or any of the calendar fields are inconsistent
    //  *            with the given date specifiers in non-lenient mode
    //  * @exception UnsupportedOperationException
    //  *            if any week year numbering isn't supported in this
    //  *            {@code Calendar}.
    //  * @see #isWeekDateSupported()
    //  * @see #getFirstDayOfWeek()
    //  * @see #getMinimalDaysInFirstWeek()
    //  * @since 1.7
    //  */
    // void setWeekDate(int weekYear, int weekOfYear, int dayOfWeek) {
    //     throw new UnsupportedOperationException();
    // }

    // /**
    //  * Returns the number of weeks in the week year represented by this
    //  * {@code Calendar}.
    //  *
    //  * <p>The default implementation of this method throws an
    //  * {@code UnsupportedOperationException}.
    //  *
    //  * @return the number of weeks in the week year.
    //  * @exception UnsupportedOperationException
    //  *            if any week year numbering isn't supported in this
    //  *            {@code Calendar}.
    //  * @see #WEEK_OF_YEAR
    //  * @see #isWeekDateSupported()
    //  * @see #getWeekYear()
    //  * @see #getActualMaximum(int)
    //  * @since 1.7
    //  */
    // int getWeeksInWeekYear() {
    //     throw new UnsupportedOperationException();
    // }

    // /**
    //  * Returns the minimum value for the given calendar field of this
    //  * <code>Calendar</code> instance. The minimum value is defined as
    //  * the smallest value returned by the {@link #get(int) get} method
    //  * for any possible time value.  The minimum value depends on
    //  * calendar system specific parameters of the instance.
    //  *
    //  * @param field the calendar field.
    //  * @return the minimum value for the given calendar field.
    //  * @see #getMaximum(int)
    //  * @see #getGreatestMinimum(int)
    //  * @see #getLeastMaximum(int)
    //  * @see #getActualMinimum(int)
    //  * @see #getActualMaximum(int)
    //  */
    // abstract int getMinimum(int field);

    // /**
    //  * Returns the maximum value for the given calendar field of this
    //  * <code>Calendar</code> instance. The maximum value is defined as
    //  * the largest value returned by the {@link #get(int) get} method
    //  * for any possible time value. The maximum value depends on
    //  * calendar system specific parameters of the instance.
    //  *
    //  * @param field the calendar field.
    //  * @return the maximum value for the given calendar field.
    //  * @see #getMinimum(int)
    //  * @see #getGreatestMinimum(int)
    //  * @see #getLeastMaximum(int)
    //  * @see #getActualMinimum(int)
    //  * @see #getActualMaximum(int)
    //  */
    // abstract int getMaximum(int field);

    // /**
    //  * Returns the highest minimum value for the given calendar field
    //  * of this <code>Calendar</code> instance. The highest minimum
    //  * value is defined as the largest value returned by {@link
    //  * #getActualMinimum(int)} for any possible time value. The
    //  * greatest minimum value depends on calendar system specific
    //  * parameters of the instance.
    //  *
    //  * @param field the calendar field.
    //  * @return the highest minimum value for the given calendar field.
    //  * @see #getMinimum(int)
    //  * @see #getMaximum(int)
    //  * @see #getLeastMaximum(int)
    //  * @see #getActualMinimum(int)
    //  * @see #getActualMaximum(int)
    //  */
    // abstract int getGreatestMinimum(int field);

    // /**
    //  * Returns the lowest maximum value for the given calendar field
    //  * of this <code>Calendar</code> instance. The lowest maximum
    //  * value is defined as the smallest value returned by {@link
    //  * #getActualMaximum(int)} for any possible time value. The least
    //  * maximum value depends on calendar system specific parameters of
    //  * the instance. For example, a <code>Calendar</code> for the
    //  * Gregorian calendar system returns 28 for the
    //  * <code>DAY_OF_MONTH</code> field, because the 28th is the last
    //  * day of the shortest month of this calendar, February in a
    //  * common year.
    //  *
    //  * @param field the calendar field.
    //  * @return the lowest maximum value for the given calendar field.
    //  * @see #getMinimum(int)
    //  * @see #getMaximum(int)
    //  * @see #getGreatestMinimum(int)
    //  * @see #getActualMinimum(int)
    //  * @see #getActualMaximum(int)
    //  */
    // abstract int getLeastMaximum(int field);

    // /**
    //  * Returns the minimum value that the specified calendar field
    //  * could have, given the time value of this <code>Calendar</code>.
    //  *
    //  * <p>The default implementation of this method uses an iterative
    //  * algorithm to determine the actual minimum value for the
    //  * calendar field. Subclasses should, if possible, override this
    //  * with a more efficient implementation - in many cases, they can
    //  * simply return <code>getMinimum()</code>.
    //  *
    //  * @param field the calendar field
    //  * @return the minimum of the given calendar field for the time
    //  * value of this <code>Calendar</code>
    //  * @see #getMinimum(int)
    //  * @see #getMaximum(int)
    //  * @see #getGreatestMinimum(int)
    //  * @see #getLeastMaximum(int)
    //  * @see #getActualMaximum(int)
    //  * @since 1.2
    //  */
    // int getActualMinimum(int field) {
    //     int fieldValue = getGreatestMinimum(field);
    //     int endValue = getMinimum(field);

    //     // if we know that the minimum value is always the same, just return it
    //     if (fieldValue == endValue) {
    //         return fieldValue;
    //     }

    //     // clone the calendar so we don't mess with the real one, and set it to
    //     // accept anything for the field values
    //     Calendar work = (Calendar)this.clone();
    //     work.setLenient(true);

    //     // now try each value from getLeastMaximum() to getMaximum() one by one until
    //     // we get a value that normalizes to another value.  The last value that
    //     // normalizes to itself is the actual minimum for the current date
    //     int result = fieldValue;

    //     do {
    //         work.set(field, fieldValue);
    //         if (work.get(field) != fieldValue) {
    //             break;
    //         } else {
    //             result = fieldValue;
    //             fieldValue--;
    //         }
    //     } while (fieldValue >= endValue);

    //     return result;
    // }

    // /**
    //  * Returns the maximum value that the specified calendar field
    //  * could have, given the time value of this
    //  * <code>Calendar</code>. For example, the actual maximum value of
    //  * the <code>MONTH</code> field is 12 in some years, and 13 in
    //  * other years in the Hebrew calendar system.
    //  *
    //  * <p>The default implementation of this method uses an iterative
    //  * algorithm to determine the actual maximum value for the
    //  * calendar field. Subclasses should, if possible, override this
    //  * with a more efficient implementation.
    //  *
    //  * @param field the calendar field
    //  * @return the maximum of the given calendar field for the time
    //  * value of this <code>Calendar</code>
    //  * @see #getMinimum(int)
    //  * @see #getMaximum(int)
    //  * @see #getGreatestMinimum(int)
    //  * @see #getLeastMaximum(int)
    //  * @see #getActualMinimum(int)
    //  * @since 1.2
    //  */
    // int getActualMaximum(int field) {
    //     int fieldValue = getLeastMaximum(field);
    //     int endValue = getMaximum(field);

    //     // if we know that the maximum value is always the same, just return it.
    //     if (fieldValue == endValue) {
    //         return fieldValue;
    //     }

    //     // clone the calendar so we don't mess with the real one, and set it to
    //     // accept anything for the field values.
    //     Calendar work = (Calendar)this.clone();
    //     work.setLenient(true);

    //     // if we're counting weeks, set the day of the week to Sunday.  We know the
    //     // last week of a month or year will contain the first day of the week.
    //     if (field == WEEK_OF_YEAR || field == WEEK_OF_MONTH) {
    //         work.set(DAY_OF_WEEK, firstDayOfWeek);
    //     }

    //     // now try each value from getLeastMaximum() to getMaximum() one by one until
    //     // we get a value that normalizes to another value.  The last value that
    //     // normalizes to itself is the actual maximum for the current date
    //     int result = fieldValue;

    //     do {
    //         work.set(field, fieldValue);
    //         if (work.get(field) != fieldValue) {
    //             break;
    //         } else {
    //             result = fieldValue;
    //             fieldValue++;
    //         }
    //     } while (fieldValue <= endValue);

    //     return result;
    // }

    // /**
    //  * Creates and returns a copy of this object.
    //  *
    //  * @return a copy of this object.
    //  */
    // @Override
    // Object clone()
    // {
    //     try {
    //         Calendar other = (Calendar) super.clone();

    //         other.fields = new int[FIELD_COUNT];
    //         other.isSet = new bool[FIELD_COUNT];
    //         other.stamp = new int[FIELD_COUNT];
    //         for (int i = 0; i < FIELD_COUNT; i++) {
    //             other.fields[i] = fields[i];
    //             other.stamp[i] = stamp[i];
    //             other.isSet[i] = isSet[i];
    //         }
    //         if (!sharedZone) {
    //             other.zone = (TimeZone) zone.clone();
    //         }
    //         return other;
    //     }
    //     catch (CloneNotSupportedException e) {
    //         // this shouldn't happen, since we are Cloneable
    //         throw new InternalError(e);
    //     }
    // }

    // private enum String[] FIELD_NAME = {
    //     "ERA", "YEAR", "MONTH", "WEEK_OF_YEAR", "WEEK_OF_MONTH", "DAY_OF_MONTH",
    //     "DAY_OF_YEAR", "DAY_OF_WEEK", "DAY_OF_WEEK_IN_MONTH", "AM_PM", "HOUR",
    //     "HOUR_OF_DAY", "MINUTE", "SECOND", "MILLISECOND", "ZONE_OFFSET",
    //     "DST_OFFSET"
    // };

    // /**
    //  * Returns the name of the specified calendar field.
    //  *
    //  * @param field the calendar field
    //  * @return the calendar field name
    //  * @exception IndexOutOfBoundsException if <code>field</code> is negative,
    //  * equal to or greater than {@code FIELD_COUNT}.
    //  */
    // static String getFieldName(int field) {
    //     return FIELD_NAME[field];
    // }

    // /**
    //  * Return a string representation of this calendar. This method
    //  * is intended to be used only for debugging purposes, and the
    //  * format of the returned string may vary between implementations.
    //  * The returned string may be empty but may not be <code>null</code>.
    //  *
    //  * @return  a string representation of this calendar.
    //  */
    // @Override
    // String toString() {
    //     // NOTE: BuddhistCalendar.toString() interprets the string
    //     // produced by this method so that the Gregorian year number
    //     // is substituted by its B.E. year value. It relies on
    //     // "...,YEAR=<year>,..." or "...,YEAR=?,...".
    //     StringBuilder buffer = new StringBuilder(800);
    //     buffer.append(getClass().getName()).append('[');
    //     appendValue(buffer, "time", isTimeSet, time);
    //     buffer.append(",areFieldsSet=").append(areFieldsSet);
    //     buffer.append(",areAllFieldsSet=").append(areAllFieldsSet);
    //     buffer.append(",lenient=").append(lenient);
    //     buffer.append(",zone=").append(zone);
    //     appendValue(buffer, ",firstDayOfWeek", true, (long) firstDayOfWeek);
    //     appendValue(buffer, ",minimalDaysInFirstWeek", true, (long) minimalDaysInFirstWeek);
    //     for (int i = 0; i < FIELD_COUNT; ++i) {
    //         buffer.append(',');
    //         appendValue(buffer, FIELD_NAME[i], isSet(i), (long) fields[i]);
    //     }
    //     buffer.append(']');
    //     return buffer.toString();
    // }

    // // =======================privates===============================

    // private static void appendValue(StringBuilder sb, String item, bool valid, long value) {
    //     sb.append(item).append('=');
    //     if (valid) {
    //         sb.append(value);
    //     } else {
    //         sb.append('?');
    //     }
    // }

    // /**
    //  * Both firstDayOfWeek and minimalDaysInFirstWeek are locale-dependent.
    //  * They are used to figure out the week count for a specific date for
    //  * a given locale. These must be set when a Calendar is constructed.
    //  * @param desiredLocale the given locale.
    //  */
    // private void setWeekCountData(Locale desiredLocale)
    // {
    //     /* try to get the Locale data from the cache */
    //     int[] data = cachedLocaleData.get(desiredLocale);
    //     if (data is null) {  /* cache miss */
    //         data = new int[2];
    //         data[0] = CalendarDataUtility.retrieveFirstDayOfWeek(desiredLocale);
    //         data[1] = CalendarDataUtility.retrieveMinimalDaysInFirstWeek(desiredLocale);
    //         cachedLocaleData.putIfAbsent(desiredLocale, data);
    //     }
    //     firstDayOfWeek = data[0];
    //     minimalDaysInFirstWeek = data[1];
    // }

    // /**
    //  * Recomputes the time and updates the status fields isTimeSet
    //  * and areFieldsSet.  Callers should check isTimeSet and only
    //  * call this method if isTimeSet is false.
    //  */
    // private void updateTime() {
    //     computeTime();
    //     // The areFieldsSet and areAllFieldsSet values are no longer
    //     // controlled here (as of 1.5).
    //     isTimeSet = true;
    // }

    // private int compareTo(long t) {
    //     long thisTime = getMillisOf(this);
    //     return (thisTime > t) ? 1 : (thisTime == t) ? 0 : -1;
    // }

    // private static long getMillisOf(Calendar calendar) {
    //     if (calendar.isTimeSet) {
    //         return calendar.time;
    //     }
    //     Calendar cal = (Calendar) calendar.clone();
    //     cal.setLenient(true);
    //     return cal.getTimeInMillis();
    // }

    // /**
    //  * Adjusts the stamp[] values before nextStamp overflow. nextStamp
    //  * is set to the next stamp value upon the return.
    //  */
    // private void adjustStamp() {
    //     int max = MINIMUM_USER_STAMP;
    //     int newStamp = MINIMUM_USER_STAMP;

    //     for (;;) {
    //         int min = Integer.MAX_VALUE;
    //         for (int v : stamp) {
    //             if (v >= newStamp && min > v) {
    //                 min = v;
    //             }
    //             if (max < v) {
    //                 max = v;
    //             }
    //         }
    //         if (max != min && min == Integer.MAX_VALUE) {
    //             break;
    //         }
    //         for (int i = 0; i < stamp.length; i++) {
    //             if (stamp[i] == min) {
    //                 stamp[i] = newStamp;
    //             }
    //         }
    //         newStamp++;
    //         if (min == max) {
    //             break;
    //         }
    //     }
    //     nextStamp = newStamp;
    // }

    // /**
    //  * Sets the WEEK_OF_MONTH and WEEK_OF_YEAR fields to new values with the
    //  * new parameter value if they have been calculated internally.
    //  */
    // private void invalidateWeekFields()
    // {
    //     if (stamp[WEEK_OF_MONTH] != COMPUTED &&
    //         stamp[WEEK_OF_YEAR] != COMPUTED) {
    //         return;
    //     }

    //     // We have to check the new values of these fields after changing
    //     // firstDayOfWeek and/or minimalDaysInFirstWeek. If the field values
    //     // have been changed, then set the new values. (4822110)
    //     Calendar cal = (Calendar) clone();
    //     cal.setLenient(true);
    //     cal.clear(WEEK_OF_MONTH);
    //     cal.clear(WEEK_OF_YEAR);

    //     if (stamp[WEEK_OF_MONTH] == COMPUTED) {
    //         int weekOfMonth = cal.get(WEEK_OF_MONTH);
    //         if (fields[WEEK_OF_MONTH] != weekOfMonth) {
    //             fields[WEEK_OF_MONTH] = weekOfMonth;
    //         }
    //     }

    //     if (stamp[WEEK_OF_YEAR] == COMPUTED) {
    //         int weekOfYear = cal.get(WEEK_OF_YEAR);
    //         if (fields[WEEK_OF_YEAR] != weekOfYear) {
    //             fields[WEEK_OF_YEAR] = weekOfYear;
    //         }
    //     }
    // }

    // /**
    //  * Save the state of this object to a stream (i.e., serialize it).
    //  *
    //  * Ideally, <code>Calendar</code> would only write out its state data and
    //  * the current time, and not write any field data out, such as
    //  * <code>fields[]</code>, <code>isTimeSet</code>, <code>areFieldsSet</code>,
    //  * and <code>isSet[]</code>.  <code>nextStamp</code> also should not be part
    //  * of the persistent state. Unfortunately, this didn't happen before JDK 1.1
    //  * shipped. To be compatible with JDK 1.1, we will always have to write out
    //  * the field values and state flags.  However, <code>nextStamp</code> can be
    //  * removed from the serialization stream; this will probably happen in the
    //  * near future.
    //  */
    // private synchronized void writeObject(ObjectOutputStream stream)
    //      throws IOException
    // {
    //     // Try to compute the time correctly, for the future (stream
    //     // version 2) in which we don't write out fields[] or isSet[].
    //     if (!isTimeSet) {
    //         try {
    //             updateTime();
    //         }
    //         catch (IllegalArgumentException e) {}
    //     }

    //     // If this Calendar has a ZoneInfo, save it and set a
    //     // SimpleTimeZone equivalent (as a single DST schedule) for
    //     // backward compatibility.
    //     TimeZone savedZone = null;
    //     if (zone instanceof ZoneInfo) {
    //         SimpleTimeZone stz = ((ZoneInfo)zone).getLastRuleInstance();
    //         if (stz is null) {
    //             stz = new SimpleTimeZone(zone.getRawOffset(), zone.getID());
    //         }
    //         savedZone = zone;
    //         zone = stz;
    //     }

    //     // Write out the 1.1 FCS object.
    //     stream.defaultWriteObject();

    //     // Write out the ZoneInfo object
    //     // 4802409: we write out even if it is null, a temporary workaround
    //     // the real fix for bug 4844924 in corba-iiop
    //     stream.writeObject(savedZone);
    //     if (savedZone !is null) {
    //         zone = savedZone;
    //     }
    // }

    // private static class CalendarAccessControlContext {
    //     private enum AccessControlContext INSTANCE;
    //     static {
    //         RuntimePermission perm = new RuntimePermission("accessClassInPackage.sun.util.calendar");
    //         PermissionCollection perms = perm.newPermissionCollection();
    //         perms.add(perm);
    //         INSTANCE = new AccessControlContext(new ProtectionDomain[] {
    //                                                 new ProtectionDomain(null, perms)
    //                                             });
    //     }
    //     private CalendarAccessControlContext() {
    //     }
    // }

    // /**
    //  * Reconstitutes this object from a stream (i.e., deserialize it).
    //  */
    // private void readObject(ObjectInputStream stream)
    //      throws IOException, ClassNotFoundException
    // {
    //     const ObjectInputStream input = stream;
    //     input.defaultReadObject();

    //     stamp = new int[FIELD_COUNT];

    //     // Starting with version 2 (not implemented yet), we expect that
    //     // fields[], isSet[], isTimeSet, and areFieldsSet may not be
    //     // streamed out anymore.  We expect 'time' to be correct.
    //     if (serialVersionOnStream >= 2)
    //     {
    //         isTimeSet = true;
    //         if (fields is null) {
    //             fields = new int[FIELD_COUNT];
    //         }
    //         if (isSet is null) {
    //             isSet = new bool[FIELD_COUNT];
    //         }
    //     }
    //     else if (serialVersionOnStream >= 0)
    //     {
    //         for (int i=0; i<FIELD_COUNT; ++i) {
    //             stamp[i] = isSet[i] ? COMPUTED : UNSET;
    //         }
    //     }

    //     serialVersionOnStream = currentSerialVersion;

    //     // If there's a ZoneInfo object, use it for zone.
    //     ZoneInfo zi = null;
    //     try {
    //         zi = AccessController.doPrivileged(
    //                 new PrivilegedExceptionAction<>() {
    //                     @Override
    //                     ZoneInfo run() throws Exception {
    //                         return (ZoneInfo) input.readObject();
    //                     }
    //                 },
    //                 CalendarAccessControlContext.INSTANCE);
    //     } catch (PrivilegedActionException pae) {
    //         Exception e = pae.getException();
    //         if (!(e instanceof OptionalDataException)) {
    //             if (e instanceof RuntimeException) {
    //                 throw (RuntimeException) e;
    //             } else if (e instanceof IOException) {
    //                 throw (IOException) e;
    //             } else if (e instanceof ClassNotFoundException) {
    //                 throw (ClassNotFoundException) e;
    //             }
    //             throw new RuntimeException(e);
    //         }
    //     }
    //     if (zi !is null) {
    //         zone = zi;
    //     }

    //     // If the deserialized object has a SimpleTimeZone, try to
    //     // replace it with a ZoneInfo equivalent (as of 1.4) in order
    //     // to be compatible with the SimpleTimeZone-based
    //     // implementation as much as possible.
    //     if (zone instanceof SimpleTimeZone) {
    //         String id = zone.getID();
    //         TimeZone tz = TimeZone.getTimeZone(id);
    //         if (tz !is null && tz.hasSameRules(zone) && tz.getID().equals(id)) {
    //             zone = tz;
    //         }
    //     }
    // }

    // /**
    //  * Converts this object to an {@link Instant}.
    //  * <p>
    //  * The conversion creates an {@code Instant} that represents the
    //  * same point on the time-line as this {@code Calendar}.
    //  *
    //  * @return the instant representing the same point on the time-line
    //  * @since 1.8
    //  */
    // const Instant toInstant() {
    //     return Instant.ofEpochMilli(getTimeInMillis());
    // }
}