Months.java
/*
* Copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
*
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package org.threeten.extra;
import static java.time.temporal.ChronoUnit.MONTHS;
import java.io.Serializable;
import java.time.DateTimeException;
import java.time.Period;
import java.time.format.DateTimeParseException;
import java.time.temporal.ChronoUnit;
import java.time.temporal.Temporal;
import java.time.temporal.TemporalAmount;
import java.time.temporal.TemporalUnit;
import java.time.temporal.UnsupportedTemporalTypeException;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.joda.convert.FromString;
import org.joda.convert.ToString;
/**
* A month-based amount of time, such as '12 months'.
* <p>
* This class models a quantity or amount of time in terms of months.
* It is a type-safe way of representing a number of months in an application.
* <p>
* The model is of a directed amount, meaning that the amount may be negative.
*
* <h3>Implementation Requirements:</h3>
* This class is immutable and thread-safe.
* <p>
* This class must be treated as a value type. Do not synchronize, rely on the
* identity hash code or use the distinction between equals() and ==.
*/
public final class Months
implements TemporalAmount, Comparable<Months>, Serializable {
/**
* A constant for zero months.
*/
public static final Months ZERO = new Months(0);
/**
* A constant for one month.
*/
public static final Months ONE = new Months(1);
/**
* A serialization identifier for this class.
*/
private static final long serialVersionUID = -8903767091325669093L;
/**
* The number of months per year.
*/
private static final int MONTHS_PER_YEAR = 12;
/**
* The pattern for parsing.
*/
private static final Pattern PATTERN =
Pattern.compile("([-+]?)P"
+ "(?:([-+]?[0-9]+)Y)?"
+ "(?:([-+]?[0-9]+)M)?", Pattern.CASE_INSENSITIVE);
/**
* The number of months.
*/
private final int months;
/**
* Obtains a {@code Months} representing a number of months.
* <p>
* The resulting amount will have the specified months.
*
* @param months the number of months, positive or negative
* @return the number of months, not null
*/
public static Months of(int months) {
if (months == 0) {
return ZERO;
} else if (months == 1) {
return ONE;
}
return new Months(months);
}
/**
* Obtains a {@code Months} representing the number of months
* equivalent to a number of years.
* <p>
* The resulting amount will be month-based, with the number of months
* equal to the number of years multiplied by 12.
*
* @param years the number of years, positive or negative
* @return the amount with the input years converted to months, not null
* @throws ArithmeticException if numeric overflow occurs
*/
public static Months ofYears(int years) {
if (years == 0) {
return ZERO;
}
return new Months(Math.multiplyExact(years, MONTHS_PER_YEAR));
}
//-----------------------------------------------------------------------
/**
* Obtains an instance of {@code Months} from a temporal amount.
* <p>
* This obtains an instance based on the specified amount.
* A {@code TemporalAmount} represents an amount of time, which may be
* date-based or time-based, which this factory extracts to a {@code Months}.
* <p>
* The result is calculated by looping around each unit in the specified amount.
* Each amount is converted to months using {@link Temporals#convertAmount}.
* If the conversion yields a remainder, an exception is thrown.
* If the amount is zero, the unit is ignored.
*
* @param amount the temporal amount to convert, not null
* @return the equivalent amount, not null
* @throws DateTimeException if unable to convert to a {@code Months}
* @throws ArithmeticException if numeric overflow occurs
*/
public static Months from(TemporalAmount amount) {
if (amount instanceof Months) {
return (Months) amount;
}
Objects.requireNonNull(amount, "amount");
int months = 0;
for (TemporalUnit unit : amount.getUnits()) {
long value = amount.get(unit);
if (value != 0) {
long[] converted = Temporals.convertAmount(value, unit, MONTHS);
if (converted[1] != 0) {
throw new DateTimeException(
"Amount could not be converted to a whole number of months: " + value + " " + unit);
}
months = Math.addExact(months, Math.toIntExact(converted[0]));
}
}
return of(months);
}
//-----------------------------------------------------------------------
/**
* Obtains a {@code Months} from a text string such as {@code PnM}.
* <p>
* This will parse the string produced by {@code toString()} which is
* based on the ISO-8601 period format {@code PnYnM}.
* <p>
* The string starts with an optional sign, denoted by the ASCII negative
* or positive symbol. If negative, the whole amount is negated.
* The ASCII letter "P" is next in upper or lower case.
* There are then two sections, each consisting of a number and a suffix.
* At least one of the two sections must be present.
* The sections have suffixes in ASCII of "Y" and "M" for years and months,
* accepted in upper or lower case. The suffixes must occur in order.
* The number part of each section must consist of ASCII digits.
* The number may be prefixed by the ASCII negative or positive symbol.
* The number must parse to an {@code int}.
* <p>
* The leading plus/minus sign, and negative values for years and months are
* not part of the ISO-8601 standard.
* <p>
* For example, the following are valid inputs:
* <pre>
* "P2M" -- Months.of(2)
* "P-2M" -- Months.of(-2)
* "-P2M" -- Months.of(-2)
* "-P-2M" -- Months.of(2)
* "P3Y" -- Months.of(3 * 12)
* "P3Y-2M" -- Months.of(3 * 12 - 2)
* </pre>
*
* @param text the text to parse, not null
* @return the parsed period, not null
* @throws DateTimeParseException if the text cannot be parsed to a period
*/
@FromString
public static Months parse(CharSequence text) {
Objects.requireNonNull(text, "text");
Matcher matcher = PATTERN.matcher(text);
if (matcher.matches()) {
int negate = "-".equals(matcher.group(1)) ? -1 : 1;
String weeksStr = matcher.group(2);
String daysStr = matcher.group(3);
if (weeksStr != null || daysStr != null) {
int months = 0;
if (daysStr != null) {
try {
months = Integer.parseInt(daysStr);
} catch (NumberFormatException ex) {
throw new DateTimeParseException("Text cannot be parsed to a Months, non-numeric months", text, 0, ex);
}
}
if (weeksStr != null) {
try {
int years = Math.multiplyExact(Integer.parseInt(weeksStr), MONTHS_PER_YEAR);
months = Math.addExact(months, years);
} catch (NumberFormatException ex) {
throw new DateTimeParseException("Text cannot be parsed to a Months, non-numeric years", text, 0, ex);
}
}
return of(Math.multiplyExact(months, negate));
}
}
throw new DateTimeParseException("Text cannot be parsed to a Months", text, 0);
}
//-----------------------------------------------------------------------
/**
* Obtains a {@code Months} consisting of the number of months between two dates.
* <p>
* The start date is included, but the end date is not.
* The result of this method can be negative if the end is before the start.
*
* @param startDateInclusive the start date, inclusive, not null
* @param endDateExclusive the end date, exclusive, not null
* @return the number of months between this date and the end date, not null
*/
public static Months between(Temporal startDateInclusive, Temporal endDateExclusive) {
return of(Math.toIntExact(MONTHS.between(startDateInclusive, endDateExclusive)));
}
//-----------------------------------------------------------------------
/**
* Constructs an instance using a specific number of months.
*
* @param months the months to use
*/
private Months(int months) {
super();
this.months = months;
}
/**
* Resolves singletons.
*
* @return the singleton instance
*/
private Object readResolve() {
return Months.of(months);
}
//-----------------------------------------------------------------------
/**
* Gets the value of the requested unit.
* <p>
* This returns a value for the supported unit - {@link ChronoUnit#MONTHS MONTHS}.
* All other units throw an exception.
*
* @param unit the {@code TemporalUnit} for which to return the value
* @return the long value of the unit
* @throws UnsupportedTemporalTypeException if the unit is not supported
*/
@Override
public long get(TemporalUnit unit) {
if (unit == MONTHS) {
return months;
}
throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
}
/**
* Gets the set of units supported by this amount.
* <p>
* The single supported unit is {@link ChronoUnit#MONTHS MONTHS}.
* <p>
* This set can be used in conjunction with {@link #get(TemporalUnit)}
* to access the entire state of the amount.
*
* @return a list containing the months unit, not null
*/
@Override
public List<TemporalUnit> getUnits() {
return Collections.singletonList(MONTHS);
}
//-----------------------------------------------------------------------
/**
* Gets the number of months in this amount.
*
* @return the number of months
*/
public int getAmount() {
return months;
}
/**
* Checks if the amount is negative.
*
* @return true if the amount is negative, false if the amount is zero or positive
*/
public boolean isNegative() {
return getAmount() < 0;
}
/**
* Checks if the amount is zero.
*
* @return true if the amount is zero, false if not
*/
public boolean isZero() {
return getAmount() == 0;
}
/**
* Checks if the amount is positive.
*
* @return true if the amount is positive, false if the amount is zero or negative
*/
public boolean isPositive() {
return getAmount() > 0;
}
//-----------------------------------------------------------------------
/**
* Returns a copy of this amount with the specified amount added.
* <p>
* The parameter is converted using {@link Months#from(TemporalAmount)}.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param amountToAdd the amount to add, not null
* @return a {@code Months} based on this instance with the requested amount added, not null
* @throws DateTimeException if the specified amount contains an invalid unit
* @throws ArithmeticException if numeric overflow occurs
*/
public Months plus(TemporalAmount amountToAdd) {
return plus(Months.from(amountToAdd).getAmount());
}
/**
* Returns a copy of this amount with the specified number of months added.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param months the amount of months to add, may be negative
* @return a {@code Months} based on this instance with the requested amount added, not null
* @throws ArithmeticException if the result overflows an int
*/
public Months plus(int months) {
if (months == 0) {
return this;
}
return of(Math.addExact(this.months, months));
}
//-----------------------------------------------------------------------
/**
* Returns a copy of this amount with the specified amount subtracted.
* <p>
* The parameter is converted using {@link Months#from(TemporalAmount)}.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param amountToSubtract the amount to subtract, not null
* @return a {@code Months} based on this instance with the requested amount subtracted, not null
* @throws DateTimeException if the specified amount contains an invalid unit
* @throws ArithmeticException if numeric overflow occurs
*/
public Months minus(TemporalAmount amountToSubtract) {
return minus(Months.from(amountToSubtract).getAmount());
}
/**
* Returns a copy of this amount with the specified number of months subtracted.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param months the amount of months to add, may be negative
* @return a {@code Months} based on this instance with the requested amount subtracted, not null
* @throws ArithmeticException if the result overflows an int
*/
public Months minus(int months) {
if (months == 0) {
return this;
}
return of(Math.subtractExact(this.months, months));
}
//-----------------------------------------------------------------------
/**
* Returns an instance with the amount multiplied by the specified scalar.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param scalar the scalar to multiply by, not null
* @return the amount multiplied by the specified scalar, not null
* @throws ArithmeticException if numeric overflow occurs
*/
public Months multipliedBy(int scalar) {
if (scalar == 1) {
return this;
}
return of(Math.multiplyExact(months, scalar));
}
/**
* Returns an instance with the amount divided by the specified divisor.
* <p>
* The calculation uses integer division, thus 3 divided by 2 is 1.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @param divisor the amount to divide by, may be negative
* @return the amount divided by the specified divisor, not null
* @throws ArithmeticException if the divisor is zero
*/
public Months dividedBy(int divisor) {
if (divisor == 1) {
return this;
}
return of(months / divisor);
}
/**
* Returns an instance with the amount negated.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @return the negated amount, not null
* @throws ArithmeticException if numeric overflow occurs, which only happens if
* the amount is {@code Long.MIN_VALUE}
*/
public Months negated() {
return multipliedBy(-1);
}
/**
* Returns a copy of this duration with a positive length.
* <p>
* This method returns a positive duration by effectively removing the sign from any negative total length.
* <p>
* This instance is immutable and unaffected by this method call.
*
* @return the absolute amount, not null
* @throws ArithmeticException if numeric overflow occurs, which only happens if
* the amount is {@code Long.MIN_VALUE}
*/
public Months abs() {
return months < 0 ? negated() : this;
}
//-------------------------------------------------------------------------
/**
* Gets the number of months as a {@code Period}.
* <p>
* This returns a period with the same number of months.
*
* @return the equivalent period, not null
*/
public Period toPeriod() {
return Period.ofMonths(months);
}
//-----------------------------------------------------------------------
/**
* Adds this amount to the specified temporal object.
* <p>
* This returns a temporal object of the same observable type as the input
* with this amount added.
* <p>
* In most cases, it is clearer to reverse the calling pattern by using
* {@link Temporal#plus(TemporalAmount)}.
* <pre>
* // these two lines are equivalent, but the second approach is recommended
* dateTime = thisAmount.addTo(dateTime);
* dateTime = dateTime.plus(thisAmount);
* </pre>
* <p>
* Only non-zero amounts will be added.
* <p>
* 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 UnsupportedTemporalTypeException if the MONTHS unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public Temporal addTo(Temporal temporal) {
if (months != 0) {
temporal = temporal.plus(months, MONTHS);
}
return temporal;
}
/**
* Subtracts this amount from the specified temporal object.
* <p>
* This returns a temporal object of the same observable type as the input
* with this amount subtracted.
* <p>
* In most cases, it is clearer to reverse the calling pattern by using
* {@link Temporal#minus(TemporalAmount)}.
* <pre>
* // these two lines are equivalent, but the second approach is recommended
* dateTime = thisAmount.subtractFrom(dateTime);
* dateTime = dateTime.minus(thisAmount);
* </pre>
* <p>
* Only non-zero amounts will be subtracted.
* <p>
* 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 UnsupportedTemporalTypeException if the MONTHS unit is not supported
* @throws ArithmeticException if numeric overflow occurs
*/
@Override
public Temporal subtractFrom(Temporal temporal) {
if (months != 0) {
temporal = temporal.minus(months, MONTHS);
}
return temporal;
}
//-----------------------------------------------------------------------
/**
* Compares this amount to the specified {@code Months}.
* <p>
* The comparison is based on the total length of the amounts.
* It is "consistent with equals", as defined by {@link Comparable}.
*
* @param otherAmount the other amount, not null
* @return the comparator value, negative if less, positive if greater
*/
@Override
public int compareTo(Months otherAmount) {
int thisValue = this.months;
int otherValue = otherAmount.months;
return Integer.compare(thisValue, otherValue);
}
//-----------------------------------------------------------------------
/**
* Checks if this amount is equal to the specified {@code Months}.
* <p>
* The comparison is based on the total length of the durations.
*
* @param otherAmount the other amount, null returns false
* @return true if the other amount is equal to this one
*/
@Override
public boolean equals(Object otherAmount) {
if (this == otherAmount) {
return true;
}
if (otherAmount instanceof Months) {
Months other = (Months) otherAmount;
return this.months == other.months;
}
return false;
}
/**
* A hash code for this amount.
*
* @return a suitable hash code
*/
@Override
public int hashCode() {
return months;
}
//-----------------------------------------------------------------------
/**
* Returns a string representation of the number of months.
* This will be in the format 'PnM' where n is the number of months.
*
* @return the number of months in ISO-8601 string format
*/
@Override
@ToString
public String toString() {
return "P" + months + "M";
}
}