Returns a copy of this duration with the specified duration _in milliseconds added.
!(p)
This instance is immutable and unaffected by this method call.
@param millisToAdd the milliseconds to add, positive or negative
@return a {@code Duration} based on this duration with the specified milliseconds added, not null
@throws ArithmeticException if numeric overflow occurs
Returns a copy of this duration with the specified duration _in milliseconds added. !(p) This instance is immutable and unaffected by this method call.
@param millisToAdd the milliseconds to add, positive or negative @return a {@code Duration} based on this duration with the specified milliseconds added, not null @throws ArithmeticException if numeric overflow occurs