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jtstand-common is a library derived from jcommon, used by jtstand-chart, which is derived from jfreechart
There is a newer version: 1.5.9
/*
 * Copyright (c) 2009 Albert Kurucz. 
 *
 * This file, RelativeDayOfWeekRule.java is part of JTStand.
 *
 * JTStand is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * JTStand is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with GTStand.  If not, see .
 */

package org.jfree.date;

/**
 * An annual date rule that returns a date for each year based on (a) a
 * reference rule; (b) a day of the week; and (c) a selection parameter
 * (SerialDate.PRECEDING, SerialDate.NEAREST, SerialDate.FOLLOWING).
 * 
 * For example, Good Friday can be specified as 'the Friday PRECEDING Easter 
 * Sunday'.
 *
 * @author David Gilbert
 */
public class RelativeDayOfWeekRule extends AnnualDateRule {

    /** A reference to the annual date rule on which this rule is based. */
    private AnnualDateRule subrule;

    /** 
     * The day of the week (SerialDate.MONDAY, SerialDate.TUESDAY, and so on). 
     */
    private int dayOfWeek;

    /** Specifies which day of the week (PRECEDING, NEAREST or FOLLOWING). */
    private int relative;

    /**
     * Default constructor - builds a rule for the Monday following 1 January.
     */
    public RelativeDayOfWeekRule() {
        this(new DayAndMonthRule(), SerialDate.MONDAY, SerialDate.FOLLOWING);
    }

    /**
     * Standard constructor - builds rule based on the supplied sub-rule.
     *
     * @param subrule  the rule that determines the reference date.
     * @param dayOfWeek  the day-of-the-week relative to the reference date.
     * @param relative  indicates *which* day-of-the-week (preceding, nearest 
     *                  or following).
     */
    public RelativeDayOfWeekRule(final AnnualDateRule subrule, 
            final int dayOfWeek, final int relative) {
        this.subrule = subrule;
        this.dayOfWeek = dayOfWeek;
        this.relative = relative;
    }

    /**
     * Returns the sub-rule (also called the reference rule).
     *
     * @return The annual date rule that determines the reference date for this 
     *         rule.
     */
    public AnnualDateRule getSubrule() {
        return this.subrule;
    }

    /**
     * Sets the sub-rule.
     *
     * @param subrule  the annual date rule that determines the reference date 
     *                 for this rule.
     */
    public void setSubrule(final AnnualDateRule subrule) {
        this.subrule = subrule;
    }

    /**
     * Returns the day-of-the-week for this rule.
     *
     * @return the day-of-the-week for this rule.
     */
    public int getDayOfWeek() {
        return this.dayOfWeek;
    }

    /**
     * Sets the day-of-the-week for this rule.
     *
     * @param dayOfWeek  the day-of-the-week (SerialDate.MONDAY, 
     *                   SerialDate.TUESDAY, and so on).
     */
    public void setDayOfWeek(final int dayOfWeek) {
        this.dayOfWeek = dayOfWeek;
    }

    /**
     * Returns the 'relative' attribute, that determines *which* 
     * day-of-the-week we are interested in (SerialDate.PRECEDING, 
     * SerialDate.NEAREST or SerialDate.FOLLOWING).
     *
     * @return The 'relative' attribute.
     */
    public int getRelative() {
        return this.relative;
    }

    /**
     * Sets the 'relative' attribute (SerialDate.PRECEDING, SerialDate.NEAREST,
     * SerialDate.FOLLOWING).
     *
     * @param relative  determines *which* day-of-the-week is selected by this 
     *                  rule.
     */
    public void setRelative(final int relative) {
        this.relative = relative;
    }

    /**
     * Creates a clone of this rule.
     *
     * @return a clone of this rule.
     *
     * @throws CloneNotSupportedException this should never happen.
     */
    public Object clone() throws CloneNotSupportedException {
        final RelativeDayOfWeekRule duplicate 
            = (RelativeDayOfWeekRule) super.clone();
        duplicate.subrule = (AnnualDateRule) duplicate.getSubrule().clone();
        return duplicate;
    }

    /**
     * Returns the date generated by this rule, for the specified year.
     *
     * @param year  the year (1900 <= year <= 9999).
     *
     * @return The date generated by the rule for the given year (possibly 
     *         null).
     */
    public SerialDate getDate(final int year) {

        // check argument...
        if ((year < SerialDate.MINIMUM_YEAR_SUPPORTED)
            || (year > SerialDate.MAXIMUM_YEAR_SUPPORTED)) {
            throw new IllegalArgumentException(
                "RelativeDayOfWeekRule.getDate(): year outside valid range.");
        }

        // calculate the date...
        SerialDate result = null;
        final SerialDate base = this.subrule.getDate(year);

        if (base != null) {
            switch (this.relative) {
                case(SerialDate.PRECEDING):
                    result = SerialDate.getPreviousDayOfWeek(this.dayOfWeek, 
                            base);
                    break;
                case(SerialDate.NEAREST):
                    result = SerialDate.getNearestDayOfWeek(this.dayOfWeek, 
                            base);
                    break;
                case(SerialDate.FOLLOWING):
                    result = SerialDate.getFollowingDayOfWeek(this.dayOfWeek, 
                            base);
                    break;
                default:
                    break;
            }
        }
        return result;

    }

}