Tomcat example source code file (FastDateFormat.java)

This example Tomcat source code file (FastDateFormat.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

date, date, dateformat, dateformat, fastdateformat, fastdateformat, fieldposition, parseposition, simpledateformat, string, stringbuffer, stringbuffer, text, util

The Tomcat FastDateFormat.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.util;

import java.util.Date;

import java.text.DateFormat;
import java.text.FieldPosition;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;

/**
 * Fast date formatter that caches recently formatted date information
 * and uses it to avoid too-frequent calls to the underlying
 * formatter.  Note: breaks fieldPosition param of format(Date,
 * StringBuffer, FieldPosition).  If you care about the field
 * position, call the underlying DateFormat directly.
 *
 * @author Stan Bailes
 * @author Alex Chaffee
 **/
public class FastDateFormat extends DateFormat {
    DateFormat    df;
    long          lastSec = -1;
    StringBuffer  sb      = new StringBuffer();
    FieldPosition fp      = new FieldPosition(DateFormat.MILLISECOND_FIELD);

    public FastDateFormat(DateFormat df) {
        this.df = df;
    }

    public Date parse(String text, ParsePosition pos) {
        return df.parse(text, pos);
    }

    /**
     * Note: breaks functionality of fieldPosition param. Also:
     * there's a bug in SimpleDateFormat with "S" and "SS", use "SSS"
     * instead if you want a msec field.
     **/
    public StringBuffer format(Date date, StringBuffer toAppendTo,
                               FieldPosition fieldPosition) {
        long dt = date.getTime();
        long ds = dt / 1000;
        if (ds != lastSec) {
            sb.setLength(0);
            df.format(date, sb, fp);
            lastSec = ds;
        } else {
            // munge current msec into existing string
            int ms = (int)(dt % 1000);
            int pos = fp.getEndIndex();
            int begin = fp.getBeginIndex();
            if (pos > 0) {
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                ms /= 10;
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
                ms /= 10;
                if (pos > begin)
                    sb.setCharAt(--pos, Character.forDigit(ms % 10, 10));
            }
        }
        toAppendTo.append(sb.toString());
        return toAppendTo;
    }

    public static void main(String[] args) {
        String format = "yyyy-MM-dd HH:mm:ss.SSS";
        if (args.length > 0)
            format = args[0];
        SimpleDateFormat sdf = new SimpleDateFormat(format);
        FastDateFormat fdf = new FastDateFormat(sdf);
        Date d = new Date();

        d.setTime(1); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(20); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(500); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(543); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(999); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(1050); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(2543); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(12345); System.out.println(fdf.format(d) + "\t" + sdf.format(d));
        d.setTime(12340); System.out.println(fdf.format(d) + "\t" + sdf.format(d));

        final int reps = 100000;
        {
            long start = System.currentTimeMillis();
            for (int i = 0; i < reps; i++) {
                d.setTime(System.currentTimeMillis());
                fdf.format(d);
            }
            long elap = System.currentTimeMillis() - start;
            System.out.println("fast: " + elap + " elapsed");
            System.out.println(fdf.format(d));
        }
        {
            long start = System.currentTimeMillis();
            for (int i = 0; i < reps; i++) {
                d.setTime(System.currentTimeMillis());
                sdf.format(d);
            }
            long elap = System.currentTimeMillis() - start;
            System.out.println("slow: " + elap + " elapsed");
            System.out.println(sdf.format(d));
        }
    }
}