JAVA时间工具类用法

1.获得N天前的TIMESTAMP

1 Calendar cl = Calendar.getInstance();
2 cl.add(Calendar.DAY_OF_YEAR, -7);
3 Date date = cl.getTime();
4 long time = date.getTime();
5 Timestamp timestamp = new Timestamp(time);

2.程序启动当前时间和任务执行既定时间

 1 /*
 2 delegate time
 3 */
 4 String time="20:00";
 5
 6 /*
 7 simpledateformat can parse String to Date, format Date to String
 8 */
 9 DateFormat dateFormat = new SimpleDateFormat("yy-MM-dd HH:mm");
10 DateFormat dayFormat = new SimpleDateFormat("yy-MM-dd");
11
12 Date curDate = dateFormat.parse(dayFormat.format(new Date()) + " " + time);
13
14 Long current =System.currentTimeMillis();
15 Long certain = curDate.getTime();