java 毫秒转日期

		String logkey = String.valueOf(System.currentTimeMillis());
		System.out.println(logkey);
		DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		Calendar calendar = Calendar.getInstance();
		calendar.setTimeInMillis(System.currentTimeMillis());
		System.out.println( " = " + formatter.format(calendar.getTime()));