fastdateformat.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.text.DateFormat;
import java.text.DateFormatSymbols;
import java.text.FieldPosition;
import java.text.Format;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.TimeZone;

/**
 * <p>FastDateFormat is a fast and thread-safe version of
 * {@link java.text.SimpleDateFormat}.</p>
 * 
 * <p>This class can be used as a direct replacement to
 * <code>SimpleDateFormat</code> in most formatting situations.
 * This class is especially useful in multi-threaded server environments.
 * <code>SimpleDateFormat</code> is not thread-safe in any JDK version,
 * nor will it be as Sun have closed the bug/RFE.
 * </p>
 *
 * <p>Only formatting is supported, but all patterns are compatible with
 * SimpleDateFormat (except time zones - see below).</p>
 *
 * <p>Java 1.4 introduced a new pattern letter, <code>'Z'</code>, to represent
 * time zones in RFC822 format (eg. <code>+0800</code> or <code>-1100</code>).
 * This pattern letter can be used here (on all JDK versions).</p>
 *
 * <p>In addition, the pattern <code>'ZZ'</code> has been made to represent
 * ISO8601 full format time zones (eg. <code>+08:00</code> or <code>-11:00</code>).
 * This introduces a minor incompatability with Java 1.4, but at a gain of
 * useful functionality.</p>
 *
 * @author TeaTrove project
 * @author Brian S O'Neill
 * @author Sean Schofield
 * @author Gary Gregory
 * @author Stephen Colebourne
 * @since 2.0
 * @version $Id: FastDateFormat.java,v 1.15 2003/08/18 02:22:25 bayard Exp $
 */
public class FastDateFormat extends Format {
    // A lot of the speed in this class comes from caching, but some comes
    // from the special int to StringBuffer conversion.
    //
    // The following produces a padded 2 digit number:
    //   buffer.append((char)(value / 10 + '0'));
    //   buffer.append((char)(value % 10 + '0'));
    //
    // Note that the fastest append to StringBuffer is a single char (used here).
    // Note that Integer.toString() is not called, the conversion is simply
    // taking the value and adding (mathematically) the ASCII value for '0'.
    // So, don't change this code! It works and is very fast.
    
    /**
     * FULL locale dependent date or time style.
     */
    public static final int FULL = DateFormat.FULL;
    /**
     * LONG locale dependent date or time style.
     */
    public static final int LONG = DateFormat.LONG;
    /**
     * MEDIUM locale dependent date or time style.
     */
    public static final int MEDIUM = DateFormat.MEDIUM;
    /**
     * SHORT locale dependent date or time style.
     */
    public static final int SHORT = DateFormat.SHORT;
    
    // package scoped as used by inner class
    static final double LOG_10 = Math.log(10);

    private static String cDefaultPattern;

    private static Map cInstanceCache = new HashMap(7);
    private static Map cDateInstanceCache = new HashMap(7);
    private static Map cTimeInstanceCache = new HashMap(7);
    private static Map cDateTimeInstanceCache = new HashMap(7);
    private static Map cTimeZoneDisplayCache = new HashMap(7);

    /**
     * The pattern.
     */
    private final String mPattern;
    /**
     * The time zone.
     */
    private final TimeZone mTimeZone;
    /**
     * Whether the time zone overrides any on Calendars.
     */
    private final boolean mTimeZoneForced;
    /**
     * The locale.
     */
    private final Locale mLocale;
    /**
     * Whether the locale overrides the default.
     */
    private final boolean mLocaleForced;
    /**
     * The parsed rules.
     */
    private Rule[] mRules;
    /**
     * The estimated maximum length.
     */
    private int mMaxLengthEstimate;

    //-----------------------------------------------------------------------
    /**
     * <p>Gets a formatter instance using the default pattern in the
     * default locale.</p>
     * 
     * @return a date/time formatter
     */
    public static FastDateFormat getInstance() {
        return getInstance(getDefaultPattern(), null, null);
    }

    /**
     * <p>Gets a formatter instance using the specified pattern in the
     * default locale.</p>
     * 
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     */
    public static FastDateFormat getInstance(String pattern) {
        return getInstance(pattern, null, null);
    }

    /**
     * <p>Gets a formatter instance using the specified pattern and
     * time zone.</p>
     * 
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     */
    public static FastDateFormat getInstance(String pattern, TimeZone timeZone) {
        return getInstance(pattern, timeZone, null);
    }

    /**
     * <p>Gets a formatter instance using the specified pattern and
     * locale.</p>
     * 
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @param locale  optional locale, overrides system locale
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     */
    public static FastDateFormat getInstance(String pattern, Locale locale) {
        return getInstance(pattern, null, locale);
    }

    /**
     * <p>Gets a formatter instance using the specified pattern, time zone
     * and locale.</p>
     * 
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @param locale  optional locale, overrides system locale
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     *  or <code>null</code>
     */
    public static synchronized FastDateFormat getInstance(String pattern, TimeZone timeZone, Locale locale) {
        FastDateFormat emptyFormat = new FastDateFormat(pattern, timeZone, locale);
        FastDateFormat format = (FastDateFormat) cInstanceCache.get(emptyFormat);
        if (format == null) {
            format = emptyFormat;
            format.init();  // convert shell format into usable one
            cInstanceCache.put(format, format);  // this is OK!
        }
        return format;
    }

    /**
     * <p>Gets a date formatter instance using the specified style, time
     * zone and locale.</p>
     * 
     * @param style  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date formatter
     * @throws IllegalArgumentException if the Locale has no date
     *  pattern defined
     */
    public static synchronized FastDateFormat getDateInstance(int style, TimeZone timeZone, Locale locale) {
        Object key = new Integer(style);
        if (timeZone != null) {
            key = new Pair(key, timeZone);
        }
        if (locale == null) {
            key = new Pair(key, locale);
        }

        FastDateFormat format = (FastDateFormat) cDateInstanceCache.get(key);
        if (format == null) {
            if (locale == null) {
                locale = Locale.getDefault();
            }

            try {
                SimpleDateFormat formatter = (SimpleDateFormat) DateFormat.getDateInstance(style, locale);
                String pattern = formatter.toPattern();
                format = getInstance(pattern, timeZone, locale);
                cDateInstanceCache.put(key, format);
                
            } catch (ClassCastException ex) {
                throw new IllegalArgumentException("No date pattern for locale: " + locale);
            }
        }
        return format;
    }

    /**
     * <p>Gets a time formatter instance using the specified style, time
     * zone and locale.</p>
     * 
     * @param style  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted time
     * @param locale  optional locale, overrides system locale
     * @return a localized standard time formatter
     * @throws IllegalArgumentException if the Locale has no time
     *  pattern defined
     */
    public static synchronized FastDateFormat getTimeInstance(int style, TimeZone timeZone, Locale locale) {
        Object key = new Integer(style);
        if (timeZone != null) {
            key = new Pair(key, timeZone);
        }
        if (locale != null) {
            key = new Pair(key, locale);
        }

        FastDateFormat format = (FastDateFormat) cTimeInstanceCache.get(key);
        if (format == null) {
            if (locale == null) {
                locale = Locale.getDefault();
            }

            try {
                SimpleDateFormat formatter = (SimpleDateFormat) DateFormat.getTimeInstance(style, locale);
                String pattern = formatter.toPattern();
                format = getInstance(pattern, timeZone, locale);
                cTimeInstanceCache.put(key, format);
            
            } catch (ClassCastException ex) {
                throw new IllegalArgumentException("No date pattern for locale: " + locale);
            }
        }
        return format;
    }

    /**
     * <p>Gets a date/time formatter instance using the specified style,
     * time zone and locale.</p>
     * 
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     */
    public static synchronized FastDateFormat getDateTimeInstance(
            int dateStyle, int timeStyle, TimeZone timeZone, Locale locale) {