* Measurement of time is built on units, such as years, months, days, hours, minutes and seconds. * Implementations of this interface represent those units. *
* An instance of this interface represents the unit itself, rather than an amount of the unit. * See {@link Period} for a class that represents an amount in terms of the common units. *
* The most commonly used units are defined in {@link ChronoUnit}. * Further units are supplied in {@link ISOFields}. * Units can also be written by application code by implementing this interface. *
* The unit works using double dispatch. Client code calls methods on a date-time like * {@code LocalDateTime} which check if the unit is a {@code ChronoUnit}. * If it is, then the date-time must handle it. * Otherwise, the method call is re-dispatched to the matching method in this interface. * *
* This should be in the plural and upper-first camel case, such as 'Days' or 'Minutes'. * * @return the name, not null */ String getName(); /** * Gets the duration of this unit, which may be an estimate. *
* All units return a duration measured in standard nanoseconds from this method. * For example, an hour has a duration of {@code 60 * 60 * 1,000,000,000ns}. *
* Some units may return an accurate duration while others return an estimate. * For example, days have an estimated duration due to the possibility of * daylight saving time changes. * To determine if the duration is an estimate, use {@link #isDurationEstimated()}. * * @return the duration of this unit, which may be an estimate, not null */ Duration getDuration(); /** * Checks if the duration of the unit is an estimate. *
* All units have a duration, however the duration is not always accurate. * For example, days have an estimated duration due to the possibility of * daylight saving time changes. * This method returns true if the duration is an estimate and false if it is * accurate. Note that accurate/estimated ignores leap seconds. * * @return true if the duration is estimated, false if accurate */ boolean isDurationEstimated(); //----------------------------------------------------------------------- /** * Checks if this unit is supported by the specified temporal object. *
* This checks that the implementing date-time can add/subtract this unit. * This can be used to avoid throwing an exception. *
* This default implementation derives the value using * {@link Temporal#plus(long, TemporalUnit)}. * * @param temporal the temporal object to check, not null * @return true if the unit is supported */ public default boolean isSupported(Temporal temporal) { try { temporal.plus(1, this); return true; } catch (RuntimeException ex) { try { temporal.plus(-1, this); return true; } catch (RuntimeException ex2) { return false; } } } /** * Returns a copy of the specified temporal object with the specified period added. *
* The period added is a multiple of this unit. For example, this method * could be used to add "3 days" to a date by calling this method on the * instance representing "days", passing the date and the period "3". * The period to be added may be negative, which is equivalent to subtraction. *
* There are two equivalent ways of using this method. * The first is to invoke this method directly. * The second is to use {@link Temporal#plus(long, TemporalUnit)}: *
* // these two lines are equivalent, but the second approach is recommended
* temporal = thisUnit.doPlus(temporal);
* temporal = temporal.plus(thisUnit);
*
* It is recommended to use the second approach, {@code plus(TemporalUnit)},
* as it is a lot clearer to read in code.
* * Implementations should perform any queries or calculations using the units * available in {@link ChronoUnit} or the fields available in {@link ChronoField}. * If the field is not supported a {@code DateTimeException} must be thrown. *
* Implementations must not alter the specified temporal object.
* Instead, an adjusted copy of the original must be returned.
* This provides equivalent, safe behavior for immutable and mutable implementations.
*
* @param
* The period will be positive if the second date-time is after the first, and
* negative if the second date-time is before the first.
* Call {@link SimplePeriod#abs() abs()} on the result to ensure that the result
* is always positive.
*
* The result can be queried for the {@link SimplePeriod#getAmount() amount}, the
* {@link SimplePeriod#getUnit() unit} and used directly in addition/subtraction:
*
* date = date.minus(MONTHS.between(start, end));
*
*
* @param