Date Format Cache : Date Format « Data Type « Java

Date Format Cache

// Copyright 2004-2005 Mort Bay Consulting Pty. Ltd.
// ------------------------------------------------------------------------
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at 
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.

import java.text.DateFormatSymbols;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/* ------------------------------------------------------------ */
/**  Date Format Cache.
 * Computes String representations of Dates and caches
 * the results so that subsequent requests within the same minute
 * will be fast.
 * Only format strings that contain either "ss" or "ss.SSS" are
 * handled.
 * The timezone of the date may be included as an ID with the "zzz"
 * format string or as an offset with the "ZZZ" format string.
 * If consecutive calls are frequently very different, then this
 * may be a little slower than a normal DateFormat.
 * @author Kent Johnson <>
 * @author Greg Wilkins (gregw)

public class DateCache  
    private static long __hitWindow=60*60;
    private static long __MaxMisses=10;
    private String _formatString;
    private String _tzFormatString;
    private SimpleDateFormat _tzFormat;
    private String _minFormatString;
    private SimpleDateFormat _minFormat;

    private String _secFormatString;
    private String _secFormatString0;
    private String _secFormatString1;

    private boolean _millis=false;
    private long _misses = 0;
    private long _lastMinutes = -1;
    private long _lastSeconds = -1;
    private String _lastResult = null;

    private Locale _locale  = null;
    private DateFormatSymbols _dfs  = null;

    /* ------------------------------------------------------------ */
    /** Constructor.
     * Make a DateCache that will use a default format. The default format
     * generates the same results as Date.toString().
    public DateCache()
        this("EEE MMM dd HH:mm:ss zzz yyyy");
    /* ------------------------------------------------------------ */
    /** Constructor.
     * Make a DateCache that will use the given format
    public DateCache(String format)
    /* ------------------------------------------------------------ */
    public DateCache(String format,Locale l)
        _locale = l;
    /* ------------------------------------------------------------ */
    public DateCache(String format,DateFormatSymbols s)
        _dfs = s;

    /* ------------------------------------------------------------ */
    /** Set the timezone.
     * @param tz TimeZone
    public void setTimeZone(TimeZone tz)
        if( _locale != null ) 
            _tzFormat=new SimpleDateFormat(_tzFormatString,_locale);
            _minFormat=new SimpleDateFormat(_minFormatString,_locale);
        else if( _dfs != null ) 
            _tzFormat=new SimpleDateFormat(_tzFormatString,_dfs);
            _minFormat=new SimpleDateFormat(_minFormatString,_dfs);
            _tzFormat=new SimpleDateFormat(_tzFormatString);
            _minFormat=new SimpleDateFormat(_minFormatString);

    /* ------------------------------------------------------------ */
    public TimeZone getTimeZone()
        return _tzFormat.getTimeZone();
    /* ------------------------------------------------------------ */
    /** Set the timezone.
     * @param timeZoneId TimeZoneId the ID of the zone as used by
     * TimeZone.getTimeZone(id)
    public void setTimeZoneID(String timeZoneId)
    /* ------------------------------------------------------------ */
    private void setTzFormatString(final  TimeZone tz )
        int zIndex = _formatString.indexOf( "ZZZ" );
        if( zIndex >= 0 )
            String ss1 = _formatString.substring( 0, zIndex );
            String ss2 = _formatString.substring( zIndex+3 );
            int tzOffset = tz.getRawOffset();
            StringBuffer sb = new StringBuffer(_formatString.length()+10);
            if( tzOffset >= 0 )
                sb.append( '+' );
                tzOffset = -tzOffset;
                sb.append( '-' );
            int raw = tzOffset / (1000*60);   // Convert to seconds
            int hr = raw / 60;
            int min = raw % 60;
            if( hr < 10 )
                sb.append( '0' );
            sb.append( hr );
            if( min < 10 )
                sb.append( '0' );
            sb.append( min );
            sb.append( '\'' );

    /* ------------------------------------------------------------ */
    private void setMinFormatString()
        int i = _tzFormatString.indexOf("ss.SSS");
        int l = 6;
        if (i>=0)
            i = _tzFormatString.indexOf("ss");
        // Build a formatter that formats a second format string
        // Have to replace @ with ' later due to bug in SimpleDateFormat
        String ss1=_tzFormatString.substring(0,i);
        String ss2=_tzFormatString.substring(i+l);
        _minFormatString =ss1+(_millis?"'ss.SSS'":"'ss'")+ss2;

    /* ------------------------------------------------------------ */
    /** Format a date according to our stored formatter.
     * @param inDate 
     * @return Formatted date
    public synchronized String format(Date inDate)
        return format(inDate.getTime());
    /* ------------------------------------------------------------ */
    /** Format a date according to our stored formatter.
     * @param inDate 
     * @return Formatted date
    public synchronized String format(long inDate)
        long seconds = inDate / 1000;

        // Is it not suitable to cache?
        if (seconds<_lastSeconds ||
            _lastSeconds>0 && seconds>_lastSeconds+__hitWindow)
            // It's a cache miss
            if (_misses<__MaxMisses)
                Date d = new Date(inDate);
                return _tzFormat.format(d);
        else if (_misses>0)
        // Check if we are in the same second
        // and don't care about millis
        if (_lastSeconds==seconds && !_millis)
            return _lastResult;

        Date d = new Date(inDate);
        // Check if we need a new format string
        long minutes = seconds/60;
        if (_lastMinutes != minutes)
            _lastMinutes = minutes;

            int i;
            int l;
            if (_millis)

        // Always format if we get here
        _lastSeconds = seconds;
        StringBuffer sb=new StringBuffer(_secFormatString.length());
            int s=(int)(seconds%60);
            if (s<10)
            if (_millis)
                long millis = inDate%1000;
                if (millis<10)
                else if (millis<100)
        return _lastResult;

    /* ------------------------------------------------------------ */
    /** Format to string buffer. 
     * @param inDate Date the format
     * @param buffer StringBuffer
    public void format(long inDate, StringBuffer buffer)
    /* ------------------------------------------------------------ */
    /** Get the format.
    public SimpleDateFormat getFormat()
        return _minFormat;

    /* ------------------------------------------------------------ */
    public String getFormatString()
        return _formatString;

    /* ------------------------------------------------------------ */
    public String now()
        return format(System.currentTimeMillis());


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