Java对世界不同时区timezone之间时间转换的处理方法

public class TimeZoneTransform {

 private static String dateTransformBetweenTimeZone(Date sourceDate, DateFormat formatter,
  TimeZone sourceTimeZone, TimeZone targetTimeZone) {
 Long targetTime = sourceDate.getTime() - sourceTimeZone.getRawOffset() + targetTimeZone.getRawOffset();
 return getTime(new Date(targetTime), formatter);
 }

 private static String getTime(Date date, DateFormat formatter) {
 return formatter.format(date);
 }

 private static String getTimeZone() {
 Calendar cal = Calendar.getInstance();
 // getOffset will access to offset and contains DaylightTime
 int timeZone = cal.getTimeZone().getOffset(System.currentTimeMillis()) / (3600000);
 if (timeZone >= 0) {
 return String.valueOf("+" + timeZone);
 }
 return String.valueOf(timeZone);
 }

 public static String getGMTTime(Date date, SimpleDateFormat formatter) {
 TimeZone srcTimeZone = TimeZone.getTimeZone("GMT" + getTimeZone());
 TimeZone destTimeZone = TimeZone.getTimeZone("GMT+8");

 return dateTransformBetweenTimeZone(date, formatter, srcTimeZone, destTimeZone);
 }

 public static void main(String[] args) {
 System.out.println(getGMTTime(new Date(System.currentTimeMillis()), new SimpleDateFormat()));
 }
}