Mega Code Archive
Formatter that caches formatted date information
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/*
* 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.
*/
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));
}
}
}
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