dateutils.java

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/* ====================================================================
 * The Apache Software License, Version 1.1
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 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
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package org.apache.commons.lang.time;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.TimeZone;

/**
 * <p>A suite of utilities surrounding the use of the
 * {@link java.util.Calendar} and {@link java.util.Date} object.</p>
 *
 * @author <a href="mailto:[e-mail]">Serge Knystautas</a>
 * @author Stephen Colebourne
 * @author Janek Bogucki
 * @author <a href="mailto:[e-mail]">Gary Gregory</a>
 * @since 2.0
 * @version $Id: DateUtils.java,v 1.16 2003/08/18 21:52:39 ggregory Exp $
 */
public class DateUtils {
    
    /**
     * The UTC time zone  (often referred to as GMT).
     */
    public static final TimeZone UTC_TIME_ZONE = TimeZone.getTimeZone("GMT");
    /**
     * Number of milliseconds in a standard second.
     */
    public static final int MILLIS_IN_SECOND = 1000;
    /**
     * Number of milliseconds in a standard minute.
     */
    public static final int MILLIS_IN_MINUTE = 60 * 1000;
    /**
     * Number of milliseconds in a standard hour.
     */
    public static final int MILLIS_IN_HOUR = 60 * 60 * 1000;
    /**
     * Number of milliseconds in a standard day.
     */
    public static final int MILLIS_IN_DAY = 24 * 60 * 60 * 1000;

    /**
     * This is half a month, so this represents whether a date is in the top
     * or bottom half of the month.
     */
    public final static int SEMI_MONTH = 1001;

    private static final int[][] fields = {
            {Calendar.MILLISECOND},
            {Calendar.SECOND},
            {Calendar.MINUTE},
            {Calendar.HOUR_OF_DAY, Calendar.HOUR},
            {Calendar.DATE, Calendar.DAY_OF_MONTH, Calendar.AM_PM /* Calendar.DAY_OF_YEAR, Calendar.DAY_OF_WEEK, Calendar.DAY_OF_WEEK_IN_MONTH */},
            {Calendar.MONTH, DateUtils.SEMI_MONTH},
            {Calendar.YEAR},
            {Calendar.ERA}};

    /**
     * A week range, starting on Sunday.
     */
    public final static int RANGE_WEEK_SUNDAY = 1;

    /**
     * A week range, starting on Monday.
     */
    public final static int RANGE_WEEK_MONDAY = 2;

    /**
     * A week range, starting on the day focused.
     */
    public final static int RANGE_WEEK_RELATIVE = 3;

    /**
     * A week range, centered around the day focused.
     */
    public final static int RANGE_WEEK_CENTER = 4;

    /**
     * A month range, the week starting on Sunday.
     */
    public final static int RANGE_MONTH_SUNDAY = 5;

    /**
     * A month range, the week starting on Monday.
     */
    public final static int RANGE_MONTH_MONDAY = 6;

    /**
     * <p><code>DateUtils</code> instances should NOT be constructed in
     * standard programming. Instead, the class should be used as
     * <code>DateUtils.parse(str);</code>.</p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean
     * instance to operate.</p>
     */
    public DateUtils() {
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Round this date, leaving the field specified as the most
     * significant field.</p>
     *
     * <p>For example, if you had the datetime of 28 Mar 2002
     * 13:45:01.231, if this was passed with HOUR, it would return
     * 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it
     * would return 1 April 2002 0:00:00.000.</p>
     * 
     * @param date  the date to work with
     * @param field  the field from <code>Calendar</code>
     *  or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     */
    public static Date round(Date date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        GregorianCalendar gval = new GregorianCalendar();
        gval.setTime(date);
        modify(gval, field, true);
        return gval.getTime();
    }

    /**
     * <p>Round this date, leaving the field specified as the most
     * significant field.</p>
     *
     * <p>For example, if you had the datetime of 28 Mar 2002
     * 13:45:01.231, if this was passed with HOUR, it would return
     * 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it
     * would return 1 April 2002 0:00:00.000.</p>
     * 
     * @param date  the date to work with
     * @param field  the field from <code>Calendar</code>
     *  or <code>SEMI_MONTH</code>
     * @return the rounded date (a different object)
     * @throws IllegalArgumentException if the date is <code>null</code>
     */
    public static Calendar round(Calendar date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar rounded = (Calendar) date.clone();
        modify(rounded, field, true);
        return rounded;
    }

    /**
     * <p>Round this date, leaving the field specified as the most
     * significant field.</p>
     *
     * <p>For example, if you had the datetime of 28 Mar 2002
     * 13:45:01.231, if this was passed with HOUR, it would return
     * 28 Mar 2002 14:00:00.000. If this was passed with MONTH, it
     * would return 1 April 2002 0:00:00.000.</p>
     * 
     * @param date  the date to work with, either Date or Calendar
     * @param field  the field from <code>Calendar</code>
     *  or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     * @throws ClassCastException if the object type is not a <code>Date</code>
     *  or <code>Calendar</code>
     */
    public static Date round(Object date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        if (date instanceof Date) {
            return round((Date) date, field);
        } else if (date instanceof Calendar) {
            return round((Calendar) date, field).getTime();
        } else {
            throw new ClassCastException("Could not round " + date);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Truncate this date, leaving the field specified as the most
     * significant field.</p>
     *
     * <p>For example, if you had the datetime of 28 Mar 2002
     * 13:45:01.231, if you passed with HOUR, it would return 28 Mar
     * 2002 13:00:00.000.  If this was passed with MONTH, it would
     * return 1 Mar 2002 0:00:00.000.</p>
     * 
     * @param date  the date to work with
     * @param field  the field from <code>Calendar</code>
     *  or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date is <code>null</code>
     */
    public static Date truncate(Date date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        GregorianCalendar gval = new GregorianCalendar();
        gval.setTime(date);
        modify(gval, field, false);
        return gval.getTime();
    }

    /**
     * <p>Truncate this date, leaving the field specified as the most
     * significant field.</p>
     *
     * <p>For example, if you had the datetime of 28 Mar 2002
     * 13:45:01.231, if you passed with HOUR, it would return 28 Mar
     * 2002 13:00:00.000.  If this was passed with MONTH, it would
     * return 1 Mar 2002 0:00:00.000.</p>
     * 
     * @param date  the date to work with
     * @param field  the field from <code>Calendar</code>
     *  or <code>SEMI_MONTH</code>
     * @return the rounded date (a different object)
     * @throws IllegalArgumentException if the date is <code>null</code>
     */
    public static Calendar truncate(Calendar date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        Calendar truncated = (Calendar) date.clone();
        modify(truncated, field, false);
        return truncated;
    }

    /**
     * <p>Truncate this date, leaving the field specified as the most
     * significant field.</p>
     *
     * <p>For example, if you had the datetime of 28 Mar 2002
     * 13:45:01.231, if you passed with HOUR, it would return 28 Mar
     * 2002 13:00:00.000.  If this was passed with MONTH, it would
     * return 1 Mar 2002 0:00:00.000.</p>
     * 
     * @param date  the date to work with, either <code>Date</code>
     *  or <code>Calendar</code>
     * @param field  the field from <code>Calendar</code>
     *  or <code>SEMI_MONTH</code>
     * @return the rounded date
     * @throws IllegalArgumentException if the date
     *  is <code>null</code>
     * @throws ClassCastException if the object type is not a
     *  <code>Date</code> or <code>Calendar</code>
     */
    public static Date truncate(Object date, int field) {
        if (date == null) {
            throw new IllegalArgumentException("The date must not be null");
        }
        if (date instanceof Date) {
            return truncate((Date) date, field);
        } else if (date instanceof Calendar) {
            return truncate((Calendar) date, field).getTime();
        } else {
            throw new ClassCastException("Could not truncate " + date);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Internal calculation method.</p>
     * 
     * @param val  the calendar
     * @param field  the field constant
     * @param round  true to round, false to truncate
     */
    private static void modify(Calendar val, int field, boolean round) {
        boolean roundUp = false;
        for (int i = 0; i < fields.length; i++) {
            for (int j = 0; j < fields[i].length; j++) {
                if (fields[i][j] == field) {
                    //This is our field... we stop looping
                    if (round && roundUp) {
                        if (field == DateUtils.SEMI_MONTH) {
                            //This is a special case that's hard to generalize
                            //If the date is 1, we round up to 16, otherwise
                            //  we subtract 15 days and add 1 month
                            if (val.get(Calendar.DATE) == 1) {
                                val.add(Calendar.DATE, 15);
                            } else {
                                val.add(Calendar.DATE, -15);
                                val.add(Calendar.MONTH, 1);
                            }
                        } else {
                            //We need at add one to this field since the
                            //  last number causes us to round up
                            val.add(fields[i][0], 1);
                        }
                    }
                    return;
                }
            }
            //We have various fields that are not easy roundings
            int offset = 0;
            boolean offsetSet = false;
            //These are special types of fields that require different rounding rules