FULL PRODUCT VERSION :
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
Java HotSpot(TM) Client VM (build 1.5.0_06-b05, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Window2000, Window XP, Linux

A DESCRIPTION OF THE PROBLEM :
java.text.SimpleDateFormat.format(java.util.Date) method is inconsistent. Means get error some time in multithreaded application.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
private static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 static {dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));}

java.util.Date dt = // Create Date with Value 2006-11-08 11:27:00

dateFormat.format(dt);


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
2006-11-08 11:27:00
ACTUAL -
2006-11-08 11:27:45

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Error 2006-11-08 11:27:00: Error Message -java.lang.Exception: new vale 2006-11-08 11:27:45 is differs with from2006-11-08 11:27:00
at org.ets.test.TestDateFormat$NewThread.run(TestDateFormat.java:57)
at java.lang.Thread.run(Unknown Source)

REPRODUCIBILITY :
This bug can be reproduced rarely.

---------- BEGIN SOURCE ----------
package org.ets.test;

import java.io.PrintWriter;
import java.io.StringWriter;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

/**
 * @author Motilal Patel, ETS.org
 *
 */
public class TestDateFormat {
private static SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
static {dateFormat.setTimeZone(TimeZone.getTimeZone("GMT"));}

public static void main(String[] args) {
int size = 20000;
String[] arrValue = new String[size];
Date[] arrDate = new Date[size];
for (int i = 0; i < arrValue.length; i++) {
arrDate[i] = new Date(System.currentTimeMillis()-(i*63642355*555888*8888*90999)-(i*6666*6666*6668));
arrValue[i] = dateFormat.format(arrDate[i]);
}

NewThread[] arrTh = new NewThread[size];
for (int i = 0; i < arrTh.length; i++) {
arrTh[i] = new NewThread(arrValue[i],arrDate[i]);
}

try {
for (int i = 0; i < arrTh.length; i++) {
arrTh[i].t.join();
}
}
catch (InterruptedException e) {
System.out.println("main thread interrupted.");
}
System.out.println("Done...");
}


static class NewThread implements Runnable {
String value;
Date dt;
Thread t;
NewThread(String value,Date dt) {
this.value=value;
this.dt = dt;
t=new Thread(this, value);
t.start();
}

public void run() {
try
{
String newValue = dateFormat.format(this.dt);
if(!newValue.equals(value))
{
throw new Exception ("new vale "+newValue+" is differs with from" + value);
}

} catch(Exception ex){
StringWriter sw = new StringWriter();
ex.printStackTrace(new PrintWriter(sw));
String error = sw.toString();
System.out.println(" Error " + value+
": Error Message -" +error);
}
}
}

}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Don’t use static member for SimpleDateFormat. Create new SimpleDateFormat object for all thread. Don’t try to use SimpleDateFormat object from multiple thread.