1. Getting all available time zone information in Java

String[] availableIDs = TimeZone.getAvailableIDs();
for (String string : availableIDs) {
	System.out.println(string);
}

II. Time Zone Conversion

/*Asia/Bishkek*/
TimeZone timeZone = TimeZone.getTimeZone("Asia/Bishkek");
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
sdf.setTimeZone(timeZone);
		
String format = sdf.format(Calendar.getInstance().getTime());
System.out.println(format);
		
sdf.setTimeZone(TimeZone.getTimeZone("Asia/Shanghai"));
String format2 = sdf.format(new Date());
System.out.println(format2);

The output time of Kyrgyzstan and Beijing time are listed above. Here is the time zone for Beijing time, Asia/Shanghai.

Conversion between UTC time and local time

    public static SimpleDateFormat get(){
		return new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
	} 
    public static String getUTCTime(){
		
		/*Local time*/
		Calendar instance = Calendar.getInstance();
		/*Time zone difference*/
		int i = instance.get(Calendar.ZONE_OFFSET);
		/*Summer time difference*/
		int j = instance.get(Calendar.DST_OFFSET);
		instance.add(Calendar.MILLISECOND, -(i+j));
		int year = instance.get(Calendar.YEAR);
		int month = (instance.get(Calendar.MONTH) + 1);
		int day = instance.get(Calendar.DAY_OF_MONTH);
		int hour = instance.get(Calendar.HOUR_OF_DAY);
		int minute = instance.get(Calendar.MINUTE);
		int second = instance.get(Calendar.SECOND);
		int milliSecond = instance.get(Calendar.MILLISECOND);
		try {
			String UTCTimeString = year + "-" + (month < 10 ? "0"+month : month) + "-" + day + " " + hour + ":" + minute + ":" + second + "." + milliSecond;
			get().parse(UTCTimeString);
			return UTCTimeString;
		} catch (ParseException e) {
			e.printStackTrace();
		}
		return null;
	}

Through the above method, UTC time can be obtained.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS");
String utcTime = getUTCTime();
System.out.println(utcTime);
Date UTCDate = sdf.parse(utcTime);
System.out.println(UTCDate);
sdf.setTimeZone(TimeZone.getTimeZone("GMT-8"));//It should be noted here that this is the only way to do it.
String format3 = sdf.format(UTCDate);
System.out.println(format3);

In this way, UTC time can be converted to zero time, but it should be noted that when the transformation is done, the form of "GMT-8" can only be used, and the form of "Asia/Shanghai" does not work.