* This interface models a date-based amount of time in a calendar system. * While most calendar systems use years, months and days, some do not. * Therefore, this interface operates solely in terms of a set of supported * units that are defined by the {@code Chronology}. * The set of supported units is fixed for a given chronology. * The amount of a supported unit may be set to zero. *
* The period is modeled as a directed amount of time, meaning that individual * parts of the period may be negative. * * @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. * Subclasses should be Serializable wherever possible. * * @since 1.8 */ public interface ChronoPeriod extends TemporalAmount { /** * Obtains a {@code ChronoPeriod} consisting of amount of time between two dates. *
* The start date is included, but the end date is not. * The period is calculated using {@link ChronoLocalDate#until(ChronoLocalDate)}. * As such, the calculation is chronology specific. *
* The chronology of the first date is used. * The chronology of the second date is ignored, with the date being converted * to the target chronology system before the calculation starts. *
* The result of this method can be a negative period if the end is before the start. * In most cases, the positive/negative sign will be the same in each of the supported fields. * * @param startDateInclusive the start date, inclusive, specifying the chronology of the calculation, not null * @param endDateExclusive the end date, exclusive, in any chronology, not null * @return the period between this date and the end date, not null * @see ChronoLocalDate#until(ChronoLocalDate) */ public static ChronoPeriod between(ChronoLocalDate startDateInclusive, ChronoLocalDate endDateExclusive) { Objects.requireNonNull(startDateInclusive, "startDateInclusive"); Objects.requireNonNull(endDateExclusive, "endDateExclusive"); return startDateInclusive.until(endDateExclusive); } //----------------------------------------------------------------------- /** * Gets the value of the requested unit. *
* The supported units are chronology specific. * They will typically be {@link ChronoUnit#YEARS YEARS}, * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}. * Requesting an unsupported unit will throw an exception. * * @param unit the {@code TemporalUnit} for which to return the value * @return the long value of the unit * @throws DateTimeException if the unit is not supported * @throws UnsupportedTemporalTypeException if the unit is not supported */ @Override long get(TemporalUnit unit); /** * Gets the set of units supported by this period. *
* The supported units are chronology specific. * They will typically be {@link ChronoUnit#YEARS YEARS}, * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}. * They are returned in order from largest to smallest. *
* This set can be used in conjunction with {@link #get(TemporalUnit)}
* to access the entire state of the period.
*
* @return a list containing the supported units, not null
*/
@Override
List
* The period is defined by the chronology.
* It controls the supported units and restricts addition/subtraction
* to {@code ChronoLocalDate} instances of the same chronology.
*
* @return the chronology defining the period, not null
*/
Chronology getChronology();
//-----------------------------------------------------------------------
/**
* Checks if all the supported units of this period are zero.
*
* @return true if this period is zero-length
*/
default boolean isZero() {
for (TemporalUnit unit : getUnits()) {
if (get(unit) != 0) {
return false;
}
}
return true;
}
/**
* Checks if any of the supported units of this period are negative.
*
* @return true if any unit of this period is negative
*/
default boolean isNegative() {
for (TemporalUnit unit : getUnits()) {
if (get(unit) < 0) {
return true;
}
}
return false;
}
//-----------------------------------------------------------------------
/**
* Returns a copy of this period with the specified period added.
*
* If the specified amount is a {@code ChronoPeriod} then it must have
* the same chronology as this period. Implementations may choose to
* accept or reject other {@code TemporalAmount} implementations.
*
* This instance is immutable and unaffected by this method call.
*
* @param amountToAdd the period to add, not null
* @return a {@code ChronoPeriod} based on this period with the requested period added, not null
* @throws ArithmeticException if numeric overflow occurs
*/
ChronoPeriod plus(TemporalAmount amountToAdd);
/**
* Returns a copy of this period with the specified period subtracted.
*
* If the specified amount is a {@code ChronoPeriod} then it must have
* the same chronology as this period. Implementations may choose to
* accept or reject other {@code TemporalAmount} implementations.
*
* This instance is immutable and unaffected by this method call.
*
* @param amountToSubtract the period to subtract, not null
* @return a {@code ChronoPeriod} based on this period with the requested period subtracted, not null
* @throws ArithmeticException if numeric overflow occurs
*/
ChronoPeriod minus(TemporalAmount amountToSubtract);
//-----------------------------------------------------------------------
/**
* Returns a new instance with each amount in this period in this period
* multiplied by the specified scalar.
*
* This returns a period with each supported unit individually multiplied.
* For example, a period of "2 years, -3 months and 4 days" multiplied by
* 3 will return "6 years, -9 months and 12 days".
* No normalization is performed.
*
* @param scalar the scalar to multiply by, not null
* @return a {@code ChronoPeriod} based on this period with the amounts multiplied
* by the scalar, not null
* @throws ArithmeticException if numeric overflow occurs
*/
ChronoPeriod multipliedBy(int scalar);
/**
* Returns a new instance with each amount in this period negated.
*
* This returns a period with each supported unit individually negated.
* For example, a period of "2 years, -3 months and 4 days" will be
* negated to "-2 years, 3 months and -4 days".
* No normalization is performed.
*
* @return a {@code ChronoPeriod} based on this period with the amounts negated, not null
* @throws ArithmeticException if numeric overflow occurs, which only happens if
* one of the units has the value {@code Long.MIN_VALUE}
*/
default ChronoPeriod negated() {
return multipliedBy(-1);
}
//-----------------------------------------------------------------------
/**
* Returns a copy of this period with the amounts of each unit normalized.
*
* The process of normalization is specific to each calendar system.
* For example, in the ISO calendar system, the years and months are
* normalized but the days are not, such that "15 months" would be
* normalized to "1 year and 3 months".
*
* This instance is immutable and unaffected by this method call.
*
* @return a {@code ChronoPeriod} based on this period with the amounts of each
* unit normalized, not null
* @throws ArithmeticException if numeric overflow occurs
*/
ChronoPeriod normalized();
//-------------------------------------------------------------------------
/**
* Adds this period to the specified temporal object.
*
* This returns a temporal object of the same observable type as the input
* with this period added.
*
* In most cases, it is clearer to reverse the calling pattern by using
* {@link Temporal#plus(TemporalAmount)}.
*
* The specified temporal must have the same chronology as this period.
* This returns a temporal with the non-zero supported units added.
*
* This instance is immutable and unaffected by this method call.
*
* @param temporal the temporal object to adjust, not null
* @return an object of the same type with the adjustment made, not null
* @throws DateTimeException if unable to add
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
Temporal addTo(Temporal temporal);
/**
* Subtracts this period from the specified temporal object.
*
* This returns a temporal object of the same observable type as the input
* with this period subtracted.
*
* In most cases, it is clearer to reverse the calling pattern by using
* {@link Temporal#minus(TemporalAmount)}.
*
* The specified temporal must have the same chronology as this period.
* This returns a temporal with the non-zero supported units subtracted.
*
* This instance is immutable and unaffected by this method call.
*
* @param temporal the temporal object to adjust, not null
* @return an object of the same type with the adjustment made, not null
* @throws DateTimeException if unable to subtract
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
Temporal subtractFrom(Temporal temporal);
//-----------------------------------------------------------------------
/**
* Checks if this period is equal to another period, including the chronology.
*
* Compares this period with another ensuring that the type, each amount and
* the chronology are the same.
* Note that this means that a period of "15 Months" is not equal to a period
* of "1 Year and 3 Months".
*
* @param obj the object to check, null returns false
* @return true if this is equal to the other period
*/
@Override
boolean equals(Object obj);
/**
* A hash code for this period.
*
* @return a suitable hash code
*/
@Override
int hashCode();
//-----------------------------------------------------------------------
/**
* Outputs this period as a {@code String}.
*
* The output will include the period amounts and chronology.
*
* @return a string representation of this period, not null
*/
@Override
String toString();
}
* // these two lines are equivalent, but the second approach is recommended
* dateTime = thisPeriod.addTo(dateTime);
* dateTime = dateTime.plus(thisPeriod);
*
*
* // these two lines are equivalent, but the second approach is recommended
* dateTime = thisPeriod.subtractFrom(dateTime);
* dateTime = dateTime.minus(thisPeriod);
*
*