將毫秒轉換成日期 再將日期轉換成毫秒程式碼：

public static void main(String[] args) throws ParseException {
		DateFormat dateFo = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
                //毫秒轉為日期
		//long currentTime = System.currentTimeMillis();//獲得現在的時間的毫秒數
		long anyTime = new Long("1316493045000");//將任意字元型的毫秒數轉換成long型
		Calendar calendar = Calendar.getInstance();
		//calendar.setTimeInMillis(currentTime);
		calendar.setTimeInMillis(anyTime);
		
		System.out.println(dateFo.format(calendar.getTime()));

		// 日期轉換為毫秒 
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		
		String dateTime = "2011-09-20 12:30:45";
		long timeInMillis = sdf.parse(dateTime).getTime();
		
		System.out.println(timeInMillis);
	}