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/*
* This file is available under and governed by the GNU General Public
* License version 2 only, as published by the Free Software Foundation.
* However, the following notice accompanied the original version of this
* file:
*
* Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
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package java.time.temporal;
import java.time.DateTimeException;
import java.time.Duration;
import java.time.LocalTime;
import java.time.Period;
import java.time.chrono.ChronoLocalDate;
import java.time.chrono.ChronoLocalDateTime;
import java.time.chrono.ChronoZonedDateTime;
/**
* A unit of date-time, such as Days or Hours.
* <p>
* Measurement of time is built on units, such as years, months, days, hours, minutes and seconds.
* Implementations of this interface represent those units.
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
*
* @implSpec
* This interface must be implemented with care to ensure other classes operate correctly.
* All implementations that can be instantiated must be final, immutable and thread-safe.
* It is recommended to use an enum where possible.
*
* @since 1.8
*/
public interface TemporalUnit {
/**
* Gets the duration of this unit, which may be an estimate.
* <p>
* All units return a duration measured in standard nanoseconds from this method.
* The duration will be positive and non-zero.
* For example, an hour has a duration of {@code 60 * 60 * 1,000,000,000ns}.
* <p>
* 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.
* <p>
* 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 represents a component of a date.
* <p>
* A date is time-based if it can be used to imply meaning from a date.
* It must have a {@linkplain #getDuration() duration} that is an integral
* multiple of the length of a standard day.
* Note that it is valid for both {@code isDateBased()} and {@code isTimeBased()}
* to return false, such as when representing a unit like 36 hours.
*
* @return true if this unit is a component of a date
*/
boolean isDateBased();
/**
* Checks if this unit represents a component of a time.
* <p>
* A unit is time-based if it can be used to imply meaning from a time.
* It must have a {@linkplain #getDuration() duration} that divides into
* the length of a standard day without remainder.
* Note that it is valid for both {@code isDateBased()} and {@code isTimeBased()}
* to return false, such as when representing a unit like 36 hours.
*
* @return true if this unit is a component of a time
*/
boolean isTimeBased();
//-----------------------------------------------------------------------
/**
* Checks if this unit is supported by the specified temporal object.
* <p>
* This checks that the implementing date-time can add/subtract this unit.
* This can be used to avoid throwing an exception.
* <p>
* 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
*/
default boolean isSupportedBy(Temporal temporal) {
if (temporal instanceof LocalTime) {
return isTimeBased();
}
if (temporal instanceof ChronoLocalDate) {
return isDateBased();
}
if (temporal instanceof ChronoLocalDateTime || temporal instanceof ChronoZonedDateTime) {
return true;
}
try {
temporal.plus(1, this);
return true;
} catch (UnsupportedTemporalTypeException ex) {
return false;
} 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.
* <p>
* 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.
* <p>
* 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)}:
* <pre>
* // these two lines are equivalent, but the second approach is recommended
* temporal = thisUnit.addTo(temporal);
* temporal = temporal.plus(thisUnit);
* </pre>
* It is recommended to use the second approach, {@code plus(TemporalUnit)},
* as it is a lot clearer to read in code.
* <p>
* Implementations should perform any queries or calculations using the units
* available in {@link ChronoUnit} or the fields available in {@link ChronoField}.
* If the unit is not supported an {@code UnsupportedTemporalTypeException} must be thrown.
* <p>
* 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 <R> the type of the Temporal object
* @param temporal the temporal object to adjust, not null
* @param amount the amount of this unit to add, positive or negative
* @return the adjusted temporal object, not null
* @throws DateTimeException if the amount cannot be added
* @throws UnsupportedTemporalTypeException if the unit is not supported by the temporal
*/
<R extends Temporal> R addTo(R temporal, long amount);
//-----------------------------------------------------------------------
/**
* Calculates the amount of time between two temporal objects.
* <p>
* This calculates the amount in terms of this unit. The start and end
* points are supplied as temporal objects and must be of compatible types.
* The implementation will convert the second type to be an instance of the
* first type before the calculating the amount.
* The result will be negative if the end is before the start.
* For example, the amount in hours between two temporal objects can be
* calculated using {@code HOURS.between(startTime, endTime)}.
* <p>
* The calculation returns a whole number, representing the number of
* complete units between the two temporals.
* For example, the amount in hours between the times 11:30 and 13:29
* will only be one hour as it is one minute short of two hours.
* <p>
* There are two equivalent ways of using this method.
* The first is to invoke this method directly.
* The second is to use {@link Temporal#until(Temporal, TemporalUnit)}:
* <pre>
* // these two lines are equivalent
* between = thisUnit.between(start, end);
* between = start.until(end, thisUnit);
* </pre>
* The choice should be made based on which makes the code more readable.
* <p>
* For example, this method allows the number of days between two dates to
* be calculated:
* <pre>
* long daysBetween = DAYS.between(start, end);
* // or alternatively
* long daysBetween = start.until(end, DAYS);
* </pre>
* <p>
* Implementations should perform any queries or calculations using the units
* available in {@link ChronoUnit} or the fields available in {@link ChronoField}.
* If the unit is not supported an {@code UnsupportedTemporalTypeException} must be thrown.
* Implementations must not alter the specified temporal objects.
*
* @implSpec
* Implementations must begin by checking to if the two temporals have the
* same type using {@code getClass()}. If they do not, then the result must be
* obtained by calling {@code temporal1Inclusive.until(temporal2Exclusive, this)}.
*
* @param temporal1Inclusive the base temporal object, not null
* @param temporal2Exclusive the other temporal object, exclusive, not null
* @return the amount of time between temporal1Inclusive and temporal2Exclusive
* in terms of this unit; positive if temporal2Exclusive is later than
* temporal1Inclusive, negative if earlier
* @throws DateTimeException if the amount cannot be calculated, or the end
* temporal cannot be converted to the same type as the start temporal
* @throws UnsupportedTemporalTypeException if the unit is not supported by the temporal
* @throws ArithmeticException if numeric overflow occurs
*/
long between(Temporal temporal1Inclusive, Temporal temporal2Exclusive);
//-----------------------------------------------------------------------
/**
* Gets a descriptive name for the unit.
* <p>
* This should be in the plural and upper-first camel case, such as 'Days' or 'Minutes'.
*
* @return the name of this unit, not null
*/
@Override
String toString();
}