java实现本地时间和格林威治时间互换

 public static String getUTCTimeByLocalTime(String localDate, String format) {
		Calendar cal = Calendar.getInstance();
		// 获得时区和 GMT-0 的时间差,偏移量
		int offset = cal.get(Calendar.ZONE_OFFSET);
		// 获得夏令时 时差
		int dstoff = cal.get(Calendar.DST_OFFSET);
		Date date = new Date(getMillSecond(format, localDate) - (offset + dstoff));// 获得当前是UTC时区的时间毫秒值
		String formatDate = format(date, format);
		return formatDate;

	}
    
    public static String getLocalTimeByUTCTime(String utcDate, String format) {
		Calendar cal = Calendar.getInstance();
		// 获得时区和 GMT-0 的时间差,偏移量
		int offset = cal.get(Calendar.ZONE_OFFSET);
		// 获得夏令时 时差
		int dstoff = cal.get(Calendar.DST_OFFSET);
		Date date = new Date(getMillSecond(format, utcDate) + (offset + dstoff));// 获得当前是UTC时区的时间毫秒值
		String formatDate = format(date, format);
		return formatDate;

	}

public static long getMillSecond(String format, String time) {
		Date parse = parse(time, format);
		return parse.getTime();
	}
	public static Date parse(String strDate, String pattern) {
		SimpleDateFormat df = new SimpleDateFormat(pattern);
		try {
			return df.parse(strDate);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
	}