ZoneOffsetTransitionRule.java

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 * Copyright (c) 2009-2012, Stephen Colebourne & Michael Nascimento Santos
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package build.tools.tzdb;

import static build.tools.tzdb.Utils.*;
import java.util.Objects;

/**
 * A rule expressing how to create a transition.
 * <p>
 * This class allows rules for identifying future transitions to be expressed.
 * A rule might be written in many forms:
 * <p><ul>
 * <li>the 16th March
 * <li>the Sunday on or after the 16th March
 * <li>the Sunday on or before the 16th March
 * <li>the last Sunday in February
 * </ul><p>
 * These different rule types can be expressed and queried.
 *
 * <h3>Specification for implementors</h3>
 * This class is immutable and thread-safe.
 *
 * @since 1.8
 */
final class ZoneOffsetTransitionRule {

    /**
     * The month of the month-day of the first day of the cutover week.
     * The actual date will be adjusted by the dowChange field.
     */
    final int month;
    /**
     * The day-of-month of the month-day of the cutover week.
     * If positive, it is the start of the week where the cutover can occur.
     * If negative, it represents the end of the week where cutover can occur.
     * The value is the number of days from the end of the month, such that
     * {@code -1} is the last day of the month, {@code -2} is the second
     * to last day, and so on.
     */
    final byte dom;
    /**
     * The cutover day-of-week, -1 to retain the day-of-month.
     */
    final int dow;
    /**
     * The cutover time in the 'before' offset.
     */
    final LocalTime time;
    /**
     * Whether the cutover time is midnight at the end of day.
     */
    final boolean timeEndOfDay;
    /**
     * The definition of how the local time should be interpreted.
     */
    final TimeDefinition timeDefinition;
    /**
     * The standard offset at the cutover.
     */
    final ZoneOffset standardOffset;
    /**
     * The offset before the cutover.
     */
    final ZoneOffset offsetBefore;
    /**
     * The offset after the cutover.
     */
    final ZoneOffset offsetAfter;

    /**
     * Creates an instance defining the yearly rule to create transitions between two offsets.
     *
     * @param month  the month of the month-day of the first day of the cutover week, from 1 to 12
     * @param dayOfMonthIndicator  the day of the month-day of the cutover week, positive if the week is that
     *  day or later, negative if the week is that day or earlier, counting from the last day of the month,
     *  from -28 to 31 excluding 0
     * @param dayOfWeek  the required day-of-week, -1 if the month-day should not be changed
     * @param time  the cutover time in the 'before' offset, not null
     * @param timeEndOfDay  whether the time is midnight at the end of day
     * @param timeDefnition  how to interpret the cutover
     * @param standardOffset  the standard offset in force at the cutover, not null
     * @param offsetBefore  the offset before the cutover, not null
     * @param offsetAfter  the offset after the cutover, not null
     * @throws IllegalArgumentException if the day of month indicator is invalid
     * @throws IllegalArgumentException if the end of day flag is true when the time is not midnight
     */
    ZoneOffsetTransitionRule(
            int month,
            int dayOfMonthIndicator,
            int dayOfWeek,
            LocalTime time,
            boolean timeEndOfDay,
            TimeDefinition timeDefnition,
            ZoneOffset standardOffset,
            ZoneOffset offsetBefore,
            ZoneOffset offsetAfter) {
        Objects.requireNonNull(time, "time");
        Objects.requireNonNull(timeDefnition, "timeDefnition");
        Objects.requireNonNull(standardOffset, "standardOffset");
        Objects.requireNonNull(offsetBefore, "offsetBefore");
        Objects.requireNonNull(offsetAfter, "offsetAfter");
        if (month < 1 || month > 12) {
            throw new IllegalArgumentException("month must be between 1 and 12");
        }
        if (dayOfMonthIndicator < -28 || dayOfMonthIndicator > 31 || dayOfMonthIndicator == 0) {
            throw new IllegalArgumentException("Day of month indicator must be between -28 and 31 inclusive excluding zero");
        }
        if (timeEndOfDay && time.equals(LocalTime.MIDNIGHT) == false) {
            throw new IllegalArgumentException("Time must be midnight when end of day flag is true");
        }
        this.month = month;
        this.dom = (byte) dayOfMonthIndicator;
        this.dow = dayOfWeek;
        this.time = time;
        this.timeEndOfDay = timeEndOfDay;
        this.timeDefinition = timeDefnition;
        this.standardOffset = standardOffset;
        this.offsetBefore = offsetBefore;
        this.offsetAfter = offsetAfter;
    }

    //-----------------------------------------------------------------------
    /**
     * Checks if this object equals another.
     * <p>
     * The entire state of the object is compared.
     *
     * @param otherRule  the other object to compare to, null returns false
     * @return true if equal
     */
    @Override
    public boolean equals(Object otherRule) {
        if (otherRule == this) {
            return true;
        }
        if (otherRule instanceof ZoneOffsetTransitionRule) {
            ZoneOffsetTransitionRule other = (ZoneOffsetTransitionRule) otherRule;
            return month == other.month && dom == other.dom && dow == other.dow &&
                timeDefinition == other.timeDefinition &&
                time.equals(other.time) &&
                timeEndOfDay == other.timeEndOfDay &&
                standardOffset.equals(other.standardOffset) &&
                offsetBefore.equals(other.offsetBefore) &&
                offsetAfter.equals(other.offsetAfter);
        }
        return false;
    }

    /**
     * Returns a suitable hash code.
     *
     * @return the hash code
     */
    @Override
    public int hashCode() {
        int hash = ((time.toSecondOfDay() + (timeEndOfDay ? 1 : 0)) << 15) +
                (month << 11) + ((dom + 32) << 5) +
                ((dow == -1 ? 8 : dow) << 2) + (timeDefinition.ordinal());
        return hash ^ standardOffset.hashCode() ^
                offsetBefore.hashCode() ^ offsetAfter.hashCode();
    }

}