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());