Java 定时任务，删除取消 Task

没有试验, 试试这个?
```java
/**
* Terminates this timer, discarding any currently scheduled tasks.
* Does not interfere with a currently executing task (if it exists).
* Once a timer has been terminated, its execution thread terminates
* gracefully, and no more tasks may be scheduled on it.
*
* <p>Note that calling this method from within the run method of a
* timer task that was invoked by this timer absolutely guarantees that
* the ongoing task execution is the last task execution that will ever
* be performed by this timer.
*
* <p>This method may be called repeatedly; the second and subsequent
* calls have no effect.
*/
public void cancel()
```

用一个线程做？

当然可以 任务提交的时候会返回一个期望， 然后 future.cancel()

每次执行完 task 再去注册 task 就行了。

直接用 schedule。

@D3EP 能否详细点，感谢

@vance 请仔细看 scheduler 的文档，里面提供的执行一次（ one shot ）的方法可以轻松的达到楼主的目的。

比如楼上 @kanepan19 提到的，你让它跑一个 callable 就能有返回值，然后下一个 trigger 根据这个返回值决定下一次怎么 schedule。

如果只用 runnable，找一个线程安全的变量来充当 flag 的作用。

还有更复杂的办法，比如你直接在项目里引用 quartz 库来达成目的也是没有问题的。

如果是 Java9，它的 forkjoin 也提供了一个定时触发异步人物的方法。

```java
public class Main {
private static final ScheduledExecutorService EXECUTOR_SERVICE = Executors.newSingleThreadScheduledExecutor();
public static void main(String[] args) {
EXECUTOR_SERVICE.schedule(Main::task, 1, TimeUnit.SECONDS);
}
public static void task(){
if (true) {
System.out.println("Continue");
EXECUTOR_SERVICE.schedule(Main::task, 1, TimeUnit.SECONDS);
}else {
System.out.println("Exit");
}
}
}
```

抛出一个运行时异常。

if(key not exist){

logger.info("直接退出执行就好了, 搞那么复杂")

return
}