定时任务的实现方式

定时任务的实现有3种方式：①while死循环 ②linux crontab ③Java TimerTask

以后补充

③还有一种不精确的方法是TimerTask。

1         TimerTask task = new TimerTask() {

2             @Override

3             public void run() {

4                 //do something

5             }

6         };

7         Timer t = new Timer();

8         t.scheduleAtFixedRate(task, 60000, 60000);

对scheduleAtFixedRate方法的解释：Timer.class的源码是这样写的。

long delay是启动这个定时任务的延迟：System.currentTimeMillis()+delay；

long period是between successive task executions.成功执行后，过period时间，再次执行一次定时任务。

 1      /*

 2      * @param task   task to be scheduled.

 3      * @param delay  delay in milliseconds before task is to be executed.

 4      * @param period time in milliseconds between successive task executions.

 5      * @throws IllegalArgumentException if <tt>delay</tt> is negative, or

 6      *         <tt>delay + System.currentTimeMillis()</tt> is negative.

 7      * @throws IllegalStateException if task was already scheduled or

 8      *         cancelled, timer was cancelled, or timer thread terminated.

 9      */

10     public void scheduleAtFixedRate(TimerTask task, long delay, long period) {

11         if (delay < 0)

12             throw new IllegalArgumentException("Negative delay.");

13         if (period <= 0)

14             throw new IllegalArgumentException("Non-positive period.");

15         sched(task, System.currentTimeMillis()+delay, period);

16     }