java gettime gmt,在java中将本地时区转换为GMT

Am trying convert date which is in local time zone to GMT, i did some thing like this

SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");

sdf.setTimeZone(TimeZone.getTimeZone("GMT"));

String gmtStrDate = sdf.format(Calendar.getInstance().getTime());

System.out.println("GMT 1"+gmtStrDate);

Date gmtDate = sdf.parse(gmtStrDate);

System.out.println("GMT 2"+gmtDate);

i am getting GMT 1 o/p in GMT tz but GMT 2 o/p is again changing to local time zone...Can any tel me why?

to get the GMT 2 o/p in GMT i did like this :

Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("GMT"));

calendar.setTime(gmtDate);

System.out.println("GMT 3 = "+calendar.getTime());

but still GMT 3o/p am getting in local tz. Please suggest on this.

解决方案

import java.util.*;

import java.text.*;

public class CurrentTimeToGMT{

public static void main(String args[]){

Date date = new Date();

DateFormat gmtFormat = new SimpleDateFormat();

TimeZone gmtTime = TimeZone.getTimeZone("GMT");

gmtFormat.setTimeZone(gmtTime);

System.out.println("Current Time: "+date);

System.out.println("GMT Time: " + gmtFormat.format(date));

}

}

Output

Current Time: Wed Mar 10 11:21:18 IST 2010

GMT Time: 3/10/10 5:51 AM