LocalDate.java

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 * file:
 *
 * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
 *
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package build.tools.tzdb;

import static build.tools.tzdb.Utils.*;
import static build.tools.tzdb.LocalTime.SECONDS_PER_DAY;
import static build.tools.tzdb.ChronoField.DAY_OF_MONTH;
import static build.tools.tzdb.ChronoField.MONTH_OF_YEAR;
import static build.tools.tzdb.ChronoField.YEAR;

import java.util.Objects;

/**
 * A date without a time-zone in the ISO-8601 calendar system,
 * such as {@code 2007-12-03}.
 *
 * @since 1.8
 */
final class LocalDate {

    /**
     * The minimum supported {@code LocalDate}, '-999999999-01-01'.
     * This could be used by an application as a "far past" date.
     */
    public static final LocalDate MIN = new LocalDate(YEAR_MIN_VALUE, 1, 1);
    /**
     * The maximum supported {@code LocalDate}, '[phone]'.
     * This could be used by an application as a "far future" date.
     */
    public static final LocalDate MAX = new LocalDate(YEAR_MAX_VALUE, 12, 31);

    /**
     * The number of days in a 400 year cycle.
     */
    private static final int DAYS_PER_CYCLE = 146097;
    /**
     * The number of days from year zero to year 1970.
     * There are five 400 year cycles from year zero to 2000.
     * There are 7 leap years from 1970 to 2000.
     */
    static final long DAYS_0000_TO_1970 = (DAYS_PER_CYCLE * 5L) - (30L * 365L + 7L);

    /**
     * The year.
     */
    private final int year;
    /**
     * The month-of-year.
     */
    private final short month;
    /**
     * The day-of-month.
     */
    private final short day;

    /**
     * Obtains an instance of {@code LocalDate} from a year, month and day.
     * <p>
     * The day must be valid for the year and month, otherwise an exception will be thrown.
     *
     * @param year  the year to represent, from MIN_YEAR to MAX_YEAR
     * @param month  the month-of-year to represent, from 1 (January) to 12 (December)
     * @param dayOfMonth  the day-of-month to represent, from 1 to 31
     * @return the local date, not null
     * @throws DateTimeException if the value of any field is out of range
     * @throws DateTimeException if the day-of-month is invalid for the month-year
     */
    public static LocalDate of(int year, int month, int dayOfMonth) {
        YEAR.checkValidValue(year);
        MONTH_OF_YEAR.checkValidValue(month);
        DAY_OF_MONTH.checkValidValue(dayOfMonth);
        if (dayOfMonth > 28 && dayOfMonth > lengthOfMonth(month, isLeapYear(year))) {
            if (dayOfMonth == 29) {
                throw new DateTimeException("Invalid date 'February 29' as '" + year + "' is not a leap year");
            } else {
                throw new DateTimeException("Invalid date '" + month + " " + dayOfMonth + "'");
            }
        }
        return new LocalDate(year, month, dayOfMonth);
    }

    /**
     * Constructor, previously validated.
     *
     * @param year  the year to represent, from MIN_YEAR to MAX_YEAR
     * @param month  the month-of-year to represent, not null
     * @param dayOfMonth  the day-of-month to represent, valid for year-month, from 1 to 31
     */
    private LocalDate(int year, int month, int dayOfMonth) {
        this.year = year;
        this.month = (short) month;
        this.day = (short) dayOfMonth;
    }

    /**
     * Gets the year field.
     * <p>
     * This method returns the primitive {@code int} value for the year.
     * <p>
     * The year returned by this method is proleptic as per {@code get(YEAR)}.
     * To obtain the year-of-era, use {@code get(YEAR_OF_ERA}.
     *
     * @return the year, from MIN_YEAR to MAX_YEAR
     */
    public int getYear() {
        return year;
    }

    /**
     * Gets the month-of-year field as an int from 1 to 12.
     *
     * @return the month-of-year
     */
    public int getMonth() {
        return month;
    }

    /**
     * Gets the day-of-month field.
     * <p>
     * This method returns the primitive {@code int} value for the day-of-month.
     *
     * @return the day-of-month, from 1 to 31
     */
    public int getDayOfMonth() {
        return day;
    }

    /**
     * Gets the day-of-week field, which is an int from 1 to 7.
     *
     * @return the day-of-week
     */
    public int getDayOfWeek() {
        return (int)floorMod(toEpochDay() + 3, 7) + 1;
    }

    /**
     * Returns a copy of this {@code LocalDate} with the specified number of days added.
     * <p>
     * This method adds the specified amount to the days field incrementing the
     * month and year fields as necessary to ensure the result remains valid.
     * The result is only invalid if the maximum/minimum year is exceeded.
     * <p>
     * For example, 2008-12-31 plus one day would result in 2009-01-01.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @param daysToAdd  the days to add, may be negative
     * @return a {@code LocalDate} based on this date with the days added, not null
     * @throws DateTimeException if the result exceeds the supported date range
     */
    public LocalDate plusDays(long daysToAdd) {
        if (daysToAdd == 0) {
            return this;
        }
        long mjDay = addExact(toEpochDay(), daysToAdd);
        return LocalDate.ofEpochDay(mjDay);
    }

    /**
     * Returns a copy of this {@code LocalDate} with the specified number of days subtracted.
     * <p>
     * This method subtracts the specified amount from the days field decrementing the
     * month and year fields as necessary to ensure the result remains valid.
     * The result is only invalid if the maximum/minimum year is exceeded.
     * <p>
     * For example, 2009-01-01 minus one day would result in 2008-12-31.
     * <p>
     * This instance is immutable and unaffected by this method call.
     *
     * @param daysToSubtract  the days to subtract, may be negative
     * @return a {@code LocalDate} based on this date with the days subtracted, not null
     * @throws DateTimeException if the result exceeds the supported date range
     */
    public LocalDate minusDays(long daysToSubtract) {
        return (daysToSubtract == Long.MIN_VALUE ? plusDays(Long.MAX_VALUE).plusDays(1) : plusDays(-daysToSubtract));
    }

    /**
     * Obtains an instance of {@code LocalDate} from the epoch day count.
     * <p>
     * The Epoch Day count is a simple incrementing count of days
     * where day 0 is 1970-01-01. Negative numbers represent earlier days.
     *
     * @param epochDay  the Epoch Day to convert, based on the epoch 1970-01-01
     * @return the local date, not null
     * @throws DateTimeException if the epoch days exceeds the supported date range
     */
    public static LocalDate ofEpochDay(long epochDay) {
        long zeroDay = epochDay + DAYS_0000_TO_1970;
        // find the march-based year
        zeroDay -= 60;  // adjust to 0000-03-01 so leap day is at end of four year cycle
        long adjust = 0;
        if (zeroDay < 0) {
            // adjust negative years to positive for calculation
            long adjustCycles = (zeroDay + 1) / DAYS_PER_CYCLE - 1;
            adjust = adjustCycles * 400;
            zeroDay += -adjustCycles * DAYS_PER_CYCLE;
        }
        long yearEst = (400 * zeroDay + 591) / DAYS_PER_CYCLE;
        long doyEst = zeroDay - (365 * yearEst + yearEst / 4 - yearEst / 100 + yearEst / 400);
        if (doyEst < 0) {
            // fix estimate
            yearEst--;
            doyEst = zeroDay - (365 * yearEst + yearEst / 4 - yearEst / 100 + yearEst / 400);
        }
        yearEst += adjust;  // reset any negative year
        int marchDoy0 = (int) doyEst;

        // convert march-based values back to january-based
        int marchMonth0 = (marchDoy0 * 5 + 2) / 153;
        int month = (marchMonth0 + 2) % 12 + 1;
        int dom = marchDoy0 - (marchMonth0 * 306 + 5) / 10 + 1;
        yearEst += marchMonth0 / 10;

        // check year now we are certain it is correct
        int year = YEAR.checkValidValue((int)yearEst);
        return new LocalDate(year, month, dom);
    }

    public long toEpochDay() {
        long y = year;
        long m = month;
        long total = 0;
        total += 365 * y;
        if (y >= 0) {
            total += (y + 3) / 4 - (y + 99) / 100 + (y + 399) / 400;
        } else {
            total -= y / -4 - y / -100 + y / -400;
        }
        total += ((367 * m - 362) / 12);
        total += day - 1;
        if (m > 2) {
            total--;
            if (isLeapYear(year) == false) {
                total--;
            }
        }
        return total - DAYS_0000_TO_1970;
    }

    /**
     * Compares this date to another date.
     * <p>
     * The comparison is primarily based on the date, from earliest to latest.
     * It is "consistent with equals", as defined by {@link Comparable}.
     * <p>
     * If all the dates being compared are instances of {@code LocalDate},
     * then the comparison will be entirely based on the date.
     * If some dates being compared are in different chronologies, then the
     * chronology is also considered, see {@link java.time.temporal.ChronoLocalDate#compareTo}.
     *
     * @param other  the other date to compare to, not null
     * @return the comparator value, negative if less, positive if greater
     */
    public int compareTo(LocalDate otherDate) {
        int cmp = (year - otherDate.year);
        if (cmp == 0) {
            cmp = (month - otherDate.month);
            if (cmp == 0) {
                cmp = (day - otherDate.day);
            }
        }
        return cmp;
    }

    /**
     * Checks if this date is equal to another date.
     * <p>
     * Compares this {@code LocalDate} with another ensuring that the date is the same.
     * <p>
     * Only objects of type {@code LocalDate} are compared, other types return false.
     * To compare the dates of two {@code TemporalAccessor} instances, including dates
     * in two different chronologies, use {@link ChronoField#EPOCH_DAY} as a comparator.
     *
     * @param obj  the object to check, null returns false
     * @return true if this is equal to the other date
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj instanceof LocalDate) {
            return compareTo((LocalDate) obj) == 0;
        }
        return false;
    }

    /**
     * A hash code for this date.
     *
     * @return a suitable hash code
     */
    @Override
    public int hashCode() {
        int yearValue = year;
        int monthValue = month;
        int dayValue = day;
        return (yearValue & 0xFFFFF800) ^ ((yearValue << 11) + (monthValue << 6) + (dayValue));
    }

}