Years.java

/*
 * Copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
 *
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package org.threeten.extra;

import static java.time.temporal.ChronoUnit.YEARS;

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 year-based amount of time, such as '12 years'.
 * <p>
 * This class models a quantity or amount of time in terms of years.
 * It is a type-safe way of representing a number of years 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 Years
        implements TemporalAmount, Comparable<Years>, Serializable {

    /**
     * A constant for zero years.
     */
    public static final Years ZERO = new Years(0);
    /**
     * A constant for one year.
     */
    public static final Years ONE = new Years(1);

    /**
     * A serialization identifier for this class.
     */
    private static final long serialVersionUID = -8903767091325669093L;
    /**
     * The pattern for parsing.
     */
    private static final Pattern PATTERN =
            Pattern.compile("([-+]?)P([-+]?[0-9]+)Y", Pattern.CASE_INSENSITIVE);

    /**
     * The number of years.
     */
    private final int years;

    /**
     * Obtains a {@code Years} representing a number of years.
     * <p>
     * The resulting amount will have the specified years.
     *
     * @param years  the number of years, positive or negative
     * @return the number of years, not null
     */
    public static Years of(int years) {
        if (years == 0) {
            return ZERO;
        } else if (years == 1) {
            return ONE;
        }
        return new Years(years);
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains an instance of {@code Years} 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 Years}.
     * <p>
     * The result is calculated by looping around each unit in the specified amount.
     * Each amount is converted to years using {@link Temporals#convertAmount}.
     * If the conversion yields a remainder, an exception is thrown.
     * If the amount is zero, the unit is ignored.
     * For example, "12 months" can be converted to years but "11 months" cannot.
     *
     * @param amount  the temporal amount to convert, not null
     * @return the equivalent amount, not null
     * @throws DateTimeException if unable to convert to a {@code Years}
     * @throws ArithmeticException if numeric overflow occurs
     */
    public static Years from(TemporalAmount amount) {
        if (amount instanceof Years) {
            return (Years) amount;
        }
        Objects.requireNonNull(amount, "amount");
        int years = 0;
        for (TemporalUnit unit : amount.getUnits()) {
            long value = amount.get(unit);
            if (value != 0) {
                long[] converted = Temporals.convertAmount(value, unit, YEARS);
                if (converted[1] != 0) {
                    throw new DateTimeException(
                            "Amount could not be converted to a whole number of years: " + value + " " + unit);
                }
                years = Math.addExact(years, Math.toIntExact(converted[0]));
            }
        }
        return of(years);
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains a {@code Years} from a text string such as {@code PnY}.
     * <p>
     * This will parse the string produced by {@code toString()} which is
     * based on the ISO-8601 period formats {@code PnY}.
     * <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.
     * The ASCII integer amount is next, which may be negative.
     * The ASCII letter "Y" is next in upper or lower case.
     * <p>
     * The leading plus/minus sign, and negative values for years are
     * not part of the ISO-8601 standard.
     * <p>
     * For example, the following are valid inputs:
     * <pre>
     *   "P2Y"             -- Years.of(2)
     *   "P-2Y"            -- Years.of(-2)
     *   "-P2Y"            -- Years.of(-2)
     *   "-P-2Y"           -- Years.of(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 Years parse(CharSequence text) {
        Objects.requireNonNull(text, "text");
        Matcher matcher = PATTERN.matcher(text);
        if (matcher.matches()) {
            int negate = "-".equals(matcher.group(1)) ? -1 : 1;
            String str = matcher.group(2);
            try {
                int val = Integer.parseInt(str);
                return of(Math.multiplyExact(val, negate));
            } catch (NumberFormatException ex) {
                throw new DateTimeParseException("Text cannot be parsed to a Years", text, 0, ex);
            }
        }
        throw new DateTimeParseException("Text cannot be parsed to a Years", text, 0);
    }

    //-----------------------------------------------------------------------
    /**
     * Obtains a {@code Years} consisting of the number of years 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 years between this date and the end date, not null
     */
    public static Years between(Temporal startDateInclusive, Temporal endDateExclusive) {
        return of(Math.toIntExact(YEARS.between(startDateInclusive, endDateExclusive)));
    }

    //-----------------------------------------------------------------------
    /**
     * Constructs an instance using a specific number of years.
     *
     * @param years  the years to use
     */
    private Years(int years) {
        super();
        this.years = years;
    }

    /**
     * Resolves singletons.
     *
     * @return the singleton instance
     */
    private Object readResolve() {
        return Years.of(years);
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the value of the requested unit.
     * <p>
     * This returns a value for the supported unit - {@link ChronoUnit#YEARS YEARS}.
     * 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 == YEARS) {
            return years;
        }
        throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
    }

    /**
     * Gets the set of units supported by this amount.
     * <p>
     * The single supported unit is {@link ChronoUnit#YEARS YEARS}.
     * <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 years unit, not null
     */
    @Override
    public List<TemporalUnit> getUnits() {
        return Collections.singletonList(YEARS);
    }

    //-----------------------------------------------------------------------
    /**
     * Gets the number of years in this amount.
     *
     * @return the number of years
     */
    public int getAmount() {
        return years;
    }

    /**
     * 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 Years#from(TemporalAmount)}.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @param amountToAdd  the amount to add, not null
     * @return a {@code Years} 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 Years plus(TemporalAmount amountToAdd) {
        return plus(Years.from(amountToAdd).getAmount());
    }

    /**
     * Returns a copy of this amount with the specified number of years added.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @param years  the amount of years to add, may be negative
     * @return a {@code Years} based on this instance with the requested amount added, not null
     * @throws ArithmeticException if the result overflows an int
     */
    public Years plus(int years) {
        if (years == 0) {
            return this;
        }
        return of(Math.addExact(this.years, years));
    }

    //-----------------------------------------------------------------------
    /**
     * Returns a copy of this amount with the specified amount subtracted.
     * <p>
     * The parameter is converted using {@link Years#from(TemporalAmount)}.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @param amountToSubtract  the amount to subtract, not null
     * @return a {@code Years} 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 Years minus(TemporalAmount amountToSubtract) {
        return minus(Years.from(amountToSubtract).getAmount());
    }

    /**
     * Returns a copy of this amount with the specified number of years subtracted.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @param years  the amount of years to add, may be negative
     * @return a {@code Years} based on this instance with the requested amount subtracted, not null
     * @throws ArithmeticException if the result overflows an int
     */
    public Years minus(int years) {
        if (years == 0) {
            return this;
        }
        return of(Math.subtractExact(this.years, years));
    }

    //-----------------------------------------------------------------------
    /**
     * 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 Years multipliedBy(int scalar) {
        if (scalar == 1) {
            return this;
        }
        return of(Math.multiplyExact(years, 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 Years dividedBy(int divisor) {
        if (divisor == 1) {
            return this;
        }
        return of(years / 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 Years 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 Years abs() {
        return years < 0 ? negated() : this;
    }

    //-------------------------------------------------------------------------
    /**
     * Gets the number of years as a {@code Period}.
     * <p>
     * This returns a period with the same number of years.
     *
     * @return the equivalent period, not null
     */
    public Period toPeriod() {
        return Period.ofYears(years);
    }

    //-----------------------------------------------------------------------
    /**
     * 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 YEARS unit is not supported
     * @throws ArithmeticException if numeric overflow occurs
     */
    @Override
    public Temporal addTo(Temporal temporal) {
        if (years != 0) {
            temporal = temporal.plus(years, YEARS);
        }
        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 YEARS unit is not supported
     * @throws ArithmeticException if numeric overflow occurs
     */
    @Override
    public Temporal subtractFrom(Temporal temporal) {
        if (years != 0) {
            temporal = temporal.minus(years, YEARS);
        }
        return temporal;
    }

    //-----------------------------------------------------------------------
    /**
     * Compares this amount to the specified {@code Years}.
     * <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(Years otherAmount) {
        int thisValue = this.years;
        int otherValue = otherAmount.years;
        return Integer.compare(thisValue, otherValue);
    }

    //-----------------------------------------------------------------------
    /**
     * Checks if this amount is equal to the specified {@code Years}.
     * <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 Years) {
            Years other = (Years) otherAmount;
            return this.years == other.years;
        }
        return false;
    }

    /**
     * A hash code for this amount.
     *
     * @return a suitable hash code
     */
    @Override
    public int hashCode() {
        return years;
    }

    //-----------------------------------------------------------------------
    /**
     * Returns a string representation of the number of years.
     * This will be in the format 'PnY' where n is the number of years.
     *
     * @return the number of years in ISO-8601 string format
     */
    @Override
    @ToString
    public String toString() {
        return "P" + years + "Y";
    }

}