Constructor accessible by subclasses.
Implementation of a clock that always returns the same _instant. This is typically used for testing.
Implementation of a clock that adds an _offset to an underlying clock.
Implementation of a clock that always returns the latest time from {@link System#currentTimeMillis()}.
Implementation of a clock that adds an _offset to an underlying clock.
Gets the time-zone being used to create dates and times. !(p) A clock will typically obtain the current _instant and then convert that to a date or time using a time-zone. This method returns the time-zone used.
Gets the current instant of the clock. !(p) This returns an instant representing the current instant as defined by the clock.
Gets the current millisecond _instant of the clock. !(p) This returns the millisecond-based _instant, measured from 1970-01-01T00:00Z (UTC). This is equivalent to the definition of {@link System#currentTimeMillis()}. !(p) Most applications should avoid this method and use {@link Instant} to represent an _instant on the time-line rather than a raw millisecond value. This method is provided to allow the use of the clock _in high performance use cases where the creation of an object would be unacceptable. !(p) The default implementation currently calls {@link #_instant}.
Checks if this clock is equal to another clock. !(p) Clocks should override this method to compare equals based on their state and to meet the contract of {@link Object#equals}. If not overridden, the behavior is defined by {@link Object#equals}
A hash code for this clock. !(p) Clocks should override this method based on their state and to meet the contract of {@link Object#hashCode}. If not overridden, the behavior is defined by {@link Object#hashCode}
Returns a copy of this clock with a different time-zone. !(p) A clock will typically obtain the current _instant and then convert that to a date or time using a time-zone. This method returns a clock with similar properties but using a different time-zone.
Obtains a clock that returns instants from the specified clock with the specified duration added !(p) This clock wraps another clock, returning instants that are later by the specified duration. If the duration is negative, the instants will be earlier than the current date and time. The main use case for this is to simulate running _in the future or _in the past. !(p) A duration of zero would have no offsetting effect. Passing zero will return the underlying clock. !(p) The returned implementation is immutable, thread-safe and {@code Serializable} providing that the base clock is.
Obtains a clock that always returns the same _instant. !(p) This clock simply returns the specified _instant. As such, it is not a clock _in the conventional sense. The main use case for this is _in testing, where the fixed clock ensures tests are not dependent on the current clock. !(p) The returned implementation is immutable, thread-safe and {@code Serializable}.
Obtains a clock that returns the current _instant using the best available system clock. !(p) This clock is based on the best available system clock. This may use {@link System#currentTimeMillis()}, or a higher resolution clock if one is available. !(p) Conversion from _instant to date or time uses the specified time-zone. !(p) The returned implementation is immutable, thread-safe and {@code Serializable}.
Obtains a clock that returns the current _instant using the best available system clock, converting to date and time using the default time-zone. !(p) This clock is based on the best available system clock. This may use {@link System#currentTimeMillis()}, or a higher resolution clock if one is available. !(p) Using this method hard codes a dependency to the default time-zone into your application. It is recommended to avoid this and use a specific time-zone whenever possible. The {@link #systemUTC() UTC clock} should be used when you need the current _instant without the date or time. !(p) The returned implementation is immutable, thread-safe and {@code Serializable}. It is equivalent to {@code system(ZoneId.systemDefault())}.
Obtains a clock that returns the current _instant using the best available system clock, converting to date and time using the UTC time-zone. !(p) This clock, rather than {@link #systemDefaultZone()}, should be used when you need the current _instant without the date or time. !(p) This clock is based on the best available system clock. This may use {@link System#currentTimeMillis()}, or a higher resolution clock if one is available. !(p) Conversion from _instant to date or time uses the {@linkplain ZoneOffset#UTC UTC time-zone}. !(p) The returned implementation is immutable, thread-safe and {@code Serializable}. It is equivalent to {@code system(ZoneOffset.UTC)}.
Obtains a clock that returns instants from the specified clock truncated to the nearest occurrence of the specified duration. !(p) This clock will only tick as per the specified duration. Thus, if the duration is half a second, the clock will return instants truncated to the half second. !(p) The tick duration must be positive. If it has a part smaller than a whole millisecond, then the whole duration must divide into one second without leaving a remainder. All normal tick durations will match these criteria, including any multiple of hours, minutes, seconds and milliseconds, and sensible nanosecond durations, such as 20ns, 250,000ns and 500,000ns. !(p) A duration of zero or one nanosecond would have no truncation effect. Passing one of these will return the underlying clock. !(p) Implementations may use a caching strategy for performance reasons. As such, it is possible that the start of the requested duration observed via this clock will be later than that observed directly via the underlying clock. !(p) The returned implementation is immutable, thread-safe and {@code Serializable} providing that the base clock is.
Obtains a clock that returns the current _instant ticking _in whole milliseconds using the best available system clock. !(p) This clock will always have the nano-of-second field truncated to milliseconds. This ensures that the visible time ticks _in whole milliseconds. The underlying clock is the best available system clock, equivalent to using {@link #system(ZoneId)}. !(p) Implementations may use a caching strategy for performance reasons. As such, it is possible that the start of the millisecond observed via this clock will be later than that observed directly via the underlying clock. !(p) The returned implementation is immutable, thread-safe and {@code Serializable}. It is equivalent to {@code tick(system(zone), Duration.ofMillis(1))}.
Obtains a clock that returns the current _instant ticking _in whole minutes using the best available system clock. !(p) This clock will always have the nano-of-second and second-of-minute fields set to zero. This ensures that the visible time ticks _in whole minutes. The underlying clock is the best available system clock, equivalent to using {@link #system(ZoneId)}. !(p) Implementations may use a caching strategy for performance reasons. As such, it is possible that the start of the minute observed via this clock will be later than that observed directly via the underlying clock. !(p) The returned implementation is immutable, thread-safe and {@code Serializable}. It is equivalent to {@code tick(system(zone), Duration.ofMinutes(1))}.
Obtains a clock that returns the current _instant ticking _in whole seconds using the best available system clock. !(p) This clock will always have the nano-of-second field set to zero. This ensures that the visible time ticks _in whole seconds. The underlying clock is the best available system clock, equivalent to using {@link #system(ZoneId)}. !(p) Implementations may use a caching strategy for performance reasons. As such, it is possible that the start of the second observed via this clock will be later than that observed directly via the underlying clock. !(p) The returned implementation is immutable, thread-safe and {@code Serializable}. It is equivalent to {@code tick(system(zone), Duration.ofSeconds(1))}.
A clock providing access to the current _instant, date and time using a time-zone. !(p) Instances of this class are used to find the current _instant, which can be interpreted using the stored time-zone to find the current date and time. As such, a clock can be used instead of {@link System#currentTimeMillis()} and {@link TimeZone#getDefault()}. !(p) Use of a {@code Clock} is optional. All key date-time classes also have a {@code now()} factory method that uses the system clock _in the default time zone. The primary purpose of this abstraction is to allow alternate clocks to be plugged _in as and when required. Applications use an object to obtain the current time rather than a static method. This can simplify testing. !(p) Best practice for applications is to pass a {@code Clock} into any method that requires the current _instant. A dependency injection framework is one way to achieve this: !(pre) class MyBean { private Clock clock; // dependency inject ... void process(LocalDate eventDate) { if (eventDate.isBefore(LocalDate.now(clock)) { ... } } } </pre> This approach allows an alternate clock, such as {@link #fixed(Instant, ZoneId) fixed} or {@link #_offset(Clock, Duration) _offset} to be used during testing. !(p) The {@code system} factory methods provide clocks based on the best available system clock This may use {@link System#currentTimeMillis()}, or a higher resolution clock if one is available.
@implSpec This abstract class must be implemented with care to ensure other classes operate correctly. All implementations that can be instantiated must be final, immutable and thread-safe. !(p) The principal methods are defined to allow the throwing of an exception. In normal use, no exceptions will be thrown, however one possible implementation would be to obtain the time from a central time server across the network. Obviously, _in this case the lookup could fail, and so the method is permitted to throw an exception. !(p) The returned instants from {@code Clock} work on a time-scale that ignores leap seconds, as described _in {@link Instant}. If the implementation wraps a source that provides leap second information, then a mechanism should be used to "smooth" the leap second. The Java Time-Scale mandates the use of UTC-SLS, however clock implementations may choose how accurate they are with the time-scale so long as they document how they work. Implementations are therefore not required to actually perform the UTC-SLS slew or to otherwise be aware of leap seconds. !(p) Implementations should implement {@code Serializable} wherever possible and must document whether or not they do support serialization.
@implNote The clock implementation provided here is based on the same underlying clock as {@link System#currentTimeMillis()}, but may have a precision finer than milliseconds if available. However, little to no guarantee is provided about the accuracy of the underlying clock. Applications requiring a more accurate clock must implement this abstract class themselves using a different external clock, such as an NTP server.
@since 1.8