serialdate.java

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/* ===================================================
 * JCommon : a free general purpose Java class library
 * ===================================================
 *
 * Project Info:  http://www.jfree.org/jcommon/index.html
 *
 * (C) Copyright 2000-2005, by Object Refinery Limited and Contributors.
 *
 * This library 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 2.1 of the License, or 
 * (at your option) any later version.
 *
 * This library 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 this library; if not, write to the Free Software Foundation, 
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * ---------------
 * SerialDate.java
 * ---------------
 * (C) Copyright 2001-2005, by Object Refinery Limited.
 *
 * Original Author:  David Gilbert (for Object Refinery Limited);
 * Contributor(s):   -;
 *
 * $Id: SerialDate.java,v 1.5 2005/06/01 14:12:28 taqua Exp $
 *
 * Changes (from 11-Oct-2001)
 * --------------------------
 * 11-Oct-2001 : Re-organised the class and moved it to new package 
 *               com.jrefinery.date (DG);
 * 05-Nov-2001 : Added a getDescription() method, and eliminated NotableDate 
 *               class (DG);
 * 12-Nov-2001 : IBD requires setDescription() method, now that NotableDate 
 *               class is gone (DG);  Changed getPreviousDayOfWeek(), 
 *               getFollowingDayOfWeek() and getNearestDayOfWeek() to correct 
 *               bugs (DG);
 * 05-Dec-2001 : Fixed bug in SpreadsheetDate class (DG);
 * 29-May-2002 : Moved the month constants into a separate interface 
 *               (MonthConstants) (DG);
 * 27-Aug-2002 : Fixed bug in addMonths() method, thanks to N???levka Petr (DG);
 * 03-Oct-2002 : Fixed errors reported by Checkstyle (DG);
 * 13-Mar-2003 : Implemented Serializable (DG);
 * 29-May-2003 : Fixed bug in addMonths method (DG);
 * 04-Sep-2003 : Implemented Comparable.  Updated the isInRange javadocs (DG);
 * 05-Jan-2005 : Fixed bug in addYears() method (1096282) (DG);
 * 
 */

package org.jfree.date;

import java.io.Serializable;
import java.text.DateFormatSymbols;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.GregorianCalendar;

/**
 *  An abstract class that defines our requirements for manipulating dates,
 *  without tying down a particular implementation.
 *  <P>
 *  Requirement 1 : match at least what Excel does for dates;
 *  Requirement 2 : class is immutable;
 *  <P>
 *  Why not just use java.util.Date?  We will, when it makes sense.  At times,
 *  java.util.Date can be *too* precise - it represents an instant in time,
 *  accurate to 1/1000th of a second (with the date itself depending on the
 *  time-zone).  Sometimes we just want to represent a particular day (e.g. 21
 *  January 2015) without concerning ourselves about the time of day, or the
 *  time-zone, or anything else.  That's what we've defined SerialDate for.
 *  <P>
 *  You can call getInstance() to get a concrete subclass of SerialDate,
 *  without worrying about the exact implementation.
 *
 * @author David Gilbert
 */
public abstract class SerialDate implements Comparable, 
                                            Serializable, 
                                            MonthConstants {

    /** For serialization. */
    private static final long serialVersionUID = -293716040467423637L;
    
    /** Date format symbols. */
    public static final DateFormatSymbols
        DATE_FORMAT_SYMBOLS = new SimpleDateFormat().getDateFormatSymbols();

    /** The serial number for 1 January 1900. */
    public static final int SERIAL_LOWER_BOUND = 2;

    /** The serial number for 31 December 9999. */
    public static final int SERIAL_UPPER_BOUND = 2958465;

    /** The lowest year value supported by this date format. */
    public static final int MINIMUM_YEAR_SUPPORTED = 1900;

    /** The highest year value supported by this date format. */
    public static final int MAXIMUM_YEAR_SUPPORTED = 9999;

    /** Useful constant for Monday. Equivalent to java.util.Calendar.MONDAY. */
    public static final int MONDAY = Calendar.MONDAY;

    /** 
     * Useful constant for Tuesday. Equivalent to java.util.Calendar.TUESDAY. 
     */
    public static final int TUESDAY = Calendar.TUESDAY;

    /** 
     * Useful constant for Wednesday. Equivalent to 
     * java.util.Calendar.WEDNESDAY. 
     */
    public static final int WEDNESDAY = Calendar.WEDNESDAY;

    /** 
     * Useful constant for Thrusday. Equivalent to java.util.Calendar.THURSDAY. 
     */
    public static final int THURSDAY = Calendar.THURSDAY;

    /** Useful constant for Friday. Equivalent to java.util.Calendar.FRIDAY. */
    public static final int FRIDAY = Calendar.FRIDAY;

    /** 
     * Useful constant for Saturday. Equivalent to java.util.Calendar.SATURDAY.
     */
    public static final int SATURDAY = Calendar.SATURDAY;

    /** Useful constant for Sunday. Equivalent to java.util.Calendar.SUNDAY. */
    public static final int SUNDAY = Calendar.SUNDAY;

    /** The number of days in each month in non leap years. */
    public static final int[] LAST_DAY_OF_MONTH =
        {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

    /** The number of days in a (non-leap) year up to the end of each month. */
    public static final int[] AGGREGATE_DAYS_TO_END_OF_MONTH =
        {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365};

    /** The number of days in a year up to the end of the preceding month. */
    public static final int[] AGGREGATE_DAYS_TO_END_OF_PRECEDING_MONTH =
        {0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365};

    /** The number of days in a leap year up to the end of each month. */
    public static final int[] LEAP_YEAR_AGGREGATE_DAYS_TO_END_OF_MONTH =
        {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366};

    /** 
     * The number of days in a leap year up to the end of the preceding month. 
     */
    public static final int[] 
        LEAP_YEAR_AGGREGATE_DAYS_TO_END_OF_PRECEDING_MONTH =
            {0, 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366};

    /** A useful constant for referring to the first week in a month. */
    public static final int FIRST_WEEK_IN_MONTH = 1;

    /** A useful constant for referring to the second week in a month. */
    public static final int SECOND_WEEK_IN_MONTH = 2;

    /** A useful constant for referring to the third week in a month. */
    public static final int THIRD_WEEK_IN_MONTH = 3;

    /** A useful constant for referring to the fourth week in a month. */
    public static final int FOURTH_WEEK_IN_MONTH = 4;

    /** A useful constant for referring to the last week in a month. */
    public static final int LAST_WEEK_IN_MONTH = 0;

    /** Useful range constant. */
    public static final int INCLUDE_NONE = 0;

    /** Useful range constant. */
    public static final int INCLUDE_FIRST = 1;

    /** Useful range constant. */
    public static final int INCLUDE_SECOND = 2;

    /** Useful range constant. */
    public static final int INCLUDE_BOTH = 3;

    /** 
     * Useful constant for specifying a day of the week relative to a fixed 
     * date. 
     */
    public static final int PRECEDING = -1;

    /** 
     * Useful constant for specifying a day of the week relative to a fixed 
     * date. 
     */
    public static final int NEAREST = 0;

    /** 
     * Useful constant for specifying a day of the week relative to a fixed 
     * date. 
     */
    public static final int FOLLOWING = 1;

    /** A description for the date. */
    private String description;

    /**
     * Default constructor.
     */
    protected SerialDate() {
    }

    /**
     * Returns true if the supplied integer code represents a valid 
     * day-of-the-week, and false otherwise.
     *
     * @param code  the code being checked for validity.
     *
     * @return true if the supplied integer code represents a valid 
     *         day-of-the-week, and false otherwise.
     */
    public static boolean isValidWeekdayCode(final int code) {

        switch(code) {
            case SUNDAY: return true;
            case MONDAY: return true;
            case TUESDAY: return true;
            case WEDNESDAY: return true;
            case THURSDAY: return true;
            case FRIDAY: return true;
            case SATURDAY: return true;
            default: return false;
        }

    }

    /**
     * Converts the supplied string to a day of the week.
     *
     * @param s  a string representing the day of the week.
     *
     * @return <code>-1</code> if the string is not convertable, the day of 
     *         the week otherwise.
     */
    public static int stringToWeekdayCode(String s) {

        final String[] shortWeekdayNames 
            = DATE_FORMAT_SYMBOLS.getShortWeekdays();
        final String[] weekDayNames = DATE_FORMAT_SYMBOLS.getWeekdays();

        int result = -1;
        s = s.trim();
        for (int i = 0; i < weekDayNames.length; i++) {
            if (s.equals(shortWeekdayNames[i])) {
                result = i;
                break;
            }
            if (s.equals(weekDayNames[i])) {
                result = i;
                break;
            }
        }
        return result;

    }

    /**
     * Returns a string representing the supplied day-of-the-week.
     * <P>
     * Need to find a better approach.
     *
     * @param weekday  the day of the week.
     *
     * @return a string representing the supplied day-of-the-week.
     */
    public static String weekdayCodeToString(final int weekday) {

        final String[] weekdays = DATE_FORMAT_SYMBOLS.getWeekdays();
        return weekdays[weekday];

    }

    /**
     * Returns an array of month names.
     *
     * @return an array of month names.
     */
    public static String[] getMonths() {

        return getMonths(false);

    }

    /**
     * Returns an array of month names.
     *
     * @param shortened  a flag indicating that shortened month names should 
     *                   be returned.
     *
     * @return an array of month names.
     */
    public static String[] getMonths(final boolean shortened) {

        if (shortened) {
            return DATE_FORMAT_SYMBOLS.getShortMonths();
        }
        else {
            return DATE_FORMAT_SYMBOLS.getMonths();
        }

    }

    /**
     * Returns true if the supplied integer code represents a valid month.
     *
     * @param code  the code being checked for validity.
     *
     * @return <code>true</code> if the supplied integer code represents a 
     *         valid month.
     */
    public static boolean isValidMonthCode(final int code) {

        switch(code) {
            case JANUARY: return true;
            case FEBRUARY: return true;
            case MARCH: return true;
            case APRIL: return true;
            case MAY: return true;
            case JUNE: return true;
            case JULY: return true;
            case AUGUST: return true;
            case SEPTEMBER: return true;
            case OCTOBER: return true;
            case NOVEMBER: return true;
            case DECEMBER: return true;
            default: return false;
        }

    }

    /**