格式化当前日期时间3种方式

1,Calendar calendar = Calendar.getInstance();String now = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(calendar.getTime()); 2,String now = new SimpleDateFormat(("yyyy-MM-dd HH:mm:ss").format(new Date()); 3,String now = new SimpleDateFormat(("yyyy-MM-dd HH:mm:ss").format(System.currentTimeMillis());