* Months is an immutable period that can only store months.
* It does not store years, days or hours for example. As such it is a
* type-safe way of representing a number of months in an application.
*
* The number of months is set in the constructor, and may be queried using
* getMonths(). Basic mathematical operations are provided -
* plus(), minus(), multipliedBy() and
* dividedBy().
*
* Months is thread-safe and immutable.
*
* @author Stephen Colebourne
* @since 1.4
*/
public final class Months extends BaseSingleFieldPeriod {
/** Constant representing zero months. */
public static final Months ZERO = new Months(0);
/** Constant representing one day. */
public static final Months ONE = new Months(1);
/** Constant representing two months. */
public static final Months TWO = new Months(2);
/** Constant representing three months. */
public static final Months THREE = new Months(3);
/** Constant representing four months. */
public static final Months FOUR = new Months(4);
/** Constant representing five months. */
public static final Months FIVE = new Months(5);
/** Constant representing six months. */
public static final Months SIX = new Months(6);
/** Constant representing seven months. */
public static final Months SEVEN = new Months(7);
/** Constant representing eight months. */
public static final Months EIGHT = new Months(8);
/** Constant representing nine months. */
public static final Months NINE = new Months(9);
/** Constant representing ten months. */
public static final Months TEN = new Months(10);
/** Constant representing eleven months. */
public static final Months ELEVEN = new Months(11);
/** Constant representing twelve months. */
public static final Months TWELVE = new Months(12);
/** Constant representing the maximum number of months that can be stored in this object. */
public static final Months MAX_VALUE = new Months(Integer.MAX_VALUE);
/** Constant representing the minimum number of months that can be stored in this object. */
public static final Months MIN_VALUE = new Months(Integer.MIN_VALUE);
/** The paser to use for this class. */
private static final PeriodFormatter PARSER = ISOPeriodFormat.standard().withParseType(PeriodType.months());
/** Serialization version. */
private static final long serialVersionUID = 87525275727380867L;
//-----------------------------------------------------------------------
/**
* Obtains an instance of Months that may be cached.
* Months is immutable, so instances can be cached and shared.
* This factory method provides access to shared instances.
*
* @param months the number of months to obtain an instance for
* @return the instance of Months
*/
public static Months months(int months) {
switch (months) {
case 0:
return ZERO;
case 1:
return ONE;
case 2:
return TWO;
case 3:
return THREE;
case 4:
return FOUR;
case 5:
return FIVE;
case 6:
return SIX;
case 7:
return SEVEN;
case 8:
return EIGHT;
case 9:
return NINE;
case 10:
return TEN;
case 11:
return ELEVEN;
case 12:
return TWELVE;
case Integer.MAX_VALUE:
return MAX_VALUE;
case Integer.MIN_VALUE:
return MIN_VALUE;
default:
return new Months(months);
}
}
//-----------------------------------------------------------------------
/**
* Creates a Months representing the number of whole months
* between the two specified datetimes. This method corectly handles
* any daylight savings time changes that may occur during the interval.
*
* @param start the start instant, must not be null
* @param end the end instant, must not be null
* @return the period in months
* @throws IllegalArgumentException if the instants are null or invalid
*/
public static Months monthsBetween(ReadableInstant start, ReadableInstant end) {
int amount = BaseSingleFieldPeriod.between(start, end, DurationFieldType.months());
return Months.months(amount);
}
/**
* Creates a Months representing the number of whole months
* between the two specified partial datetimes.
*
* The two partials must contain the same fields, for example you can specify
* two LocalDate objects.
*
* @param start the start partial date, must not be null
* @param end the end partial date, must not be null
* @return the period in months
* @throws IllegalArgumentException if the partials are null or invalid
*/
public static Months monthsBetween(ReadablePartial start, ReadablePartial end) {
if (start instanceof LocalDate && end instanceof LocalDate) {
Chronology chrono = DateTimeUtils.getChronology(start.getChronology());
int months = chrono.months().getDifference(
((LocalDate) end).getLocalMillis(), ((LocalDate) start).getLocalMillis());
return Months.months(months);
}
int amount = BaseSingleFieldPeriod.between(start, end, ZERO);
return Months.months(amount);
}
/**
* Creates a Months representing the number of whole months
* in the specified interval. This method corectly handles any daylight
* savings time changes that may occur during the interval.
*
* @param interval the interval to extract months from, null returns zero
* @return the period in months
* @throws IllegalArgumentException if the partials are null or invalid
*/
public static Months monthsIn(ReadableInterval interval) {
if (interval == null) {
return Months.ZERO;
}
int amount = BaseSingleFieldPeriod.between(interval.getStart(), interval.getEnd(), DurationFieldType.months());
return Months.months(amount);
}
/**
* Creates a new Months by parsing a string in the ISO8601 format 'PnM'.
*
* The parse will accept the full ISO syntax of PnYnMnWnDTnHnMnS however only the
* months component may be non-zero. If any other component is non-zero, an exception
* will be thrown.
*
* @param periodStr the period string, null returns zero
* @return the period in months
* @throws IllegalArgumentException if the string format is invalid
*/
public static Months parseMonths(String periodStr) {
if (periodStr == null) {
return Months.ZERO;
}
Period p = PARSER.parsePeriod(periodStr);
return Months.months(p.getMonths());
}
//-----------------------------------------------------------------------
/**
* Creates a new instance representing a number of months.
* You should consider using the factory method {@link #months(int)}
* instead of the constructor.
*
* @param months the number of months to represent
*/
private Months(int months) {
super(months);
}
/**
* Resolves singletons.
*
* @return the singleton instance
*/
private Object readResolve() {
return Months.months(getValue());
}
//-----------------------------------------------------------------------
/**
* Gets the duration field type, which is months.
*
* @return the period type
*/
public DurationFieldType getFieldType() {
return DurationFieldType.months();
}
/**
* Gets the period type, which is months.
*
* @return the period type
*/
public PeriodType getPeriodType() {
return PeriodType.months();
}
//-----------------------------------------------------------------------
/**
* Gets the number of months that this period represents.
*
* @return the number of months in the period
*/
public int getMonths() {
return getValue();
}
//-----------------------------------------------------------------------
/**
* Returns a new instance with the specified number of months added.
*
* This instance is immutable and unaffected by this method call. * * @param months the amount of months to add, may be negative * @return the new period plus the specified number of months * @throws ArithmeticException if the result overflows an int */ public Months plus(int months) { if (months == 0) { return this; } return Months.months(FieldUtils.safeAdd(getValue(), months)); } /** * Returns a new instance with the specified number of months added. *
* This instance is immutable and unaffected by this method call. * * @param months the amount of months to add, may be negative, null means zero * @return the new period plus the specified number of months * @throws ArithmeticException if the result overflows an int */ public Months plus(Months months) { if (months == null) { return this; } return plus(months.getValue()); } //----------------------------------------------------------------------- /** * Returns a new instance with the specified number of months taken away. *
* This instance is immutable and unaffected by this method call. * * @param months the amount of months to take away, may be negative * @return the new period minus the specified number of months * @throws ArithmeticException if the result overflows an int */ public Months minus(int months) { return plus(FieldUtils.safeNegate(months)); } /** * Returns a new instance with the specified number of months taken away. *
* This instance is immutable and unaffected by this method call. * * @param months the amount of months to take away, may be negative, null means zero * @return the new period minus the specified number of months * @throws ArithmeticException if the result overflows an int */ public Months minus(Months months) { if (months == null) { return this; } return minus(months.getValue()); } //----------------------------------------------------------------------- /** * Returns a new instance with the months multiplied by the specified scalar. *
* This instance is immutable and unaffected by this method call. * * @param scalar the amount to multiply by, may be negative * @return the new period multiplied by the specified scalar * @throws ArithmeticException if the result overflows an int */ public Months multipliedBy(int scalar) { return Months.months(FieldUtils.safeMultiply(getValue(), scalar)); } /** * Returns a new instance with the months divided by the specified divisor. * The calculation uses integer division, thus 3 divided by 2 is 1. *
* This instance is immutable and unaffected by this method call. * * @param divisor the amount to divide by, may be negative * @return the new period divided by the specified divisor * @throws ArithmeticException if the divisor is zero */ public Months dividedBy(int divisor) { if (divisor == 1) { return this; } return Months.months(getValue() / divisor); } //----------------------------------------------------------------------- /** * Returns a new instance with the months value negated. * * @return the new period with a negated value * @throws ArithmeticException if the result overflows an int */ public Months negated() { return Months.months(FieldUtils.safeNegate(getValue())); } //----------------------------------------------------------------------- /** * Is this months instance greater than the specified number of months. * * @param other the other period, null means zero * @return true if this months instance is greater than the specified one */ public boolean isGreaterThan(Months other) { if (other == null) { return getValue() > 0; } return getValue() > other.getValue(); } /** * Is this months instance less than the specified number of months. * * @param other the other period, null means zero * @return true if this months instance is less than the specified one */ public boolean isLessThan(Months other) { if (other == null) { return getValue() < 0; } return getValue() < other.getValue(); } //----------------------------------------------------------------------- /** * Gets this instance as a String in the ISO8601 duration format. *
* For example, "P4M" represents 4 months. * * @return the value as an ISO8601 string */ public String toString() { return "P" + String.valueOf(getValue()) + "M"; } }