private static final int QUEUE_SIZE = 20;private static final int CORE_POOL_SIZE = 2;private static final int MAX_POOL_SIZE = 2;private static final int KEEP_ALIVE_TIME = 5;  public static void main(String[] args) throws Exception {ThreadPoolExecutor executor = new ThreadPoolExecutor(CORE_POOL_SIZE, MAX_POOL_SIZE, KEEP_ALIVE_TIME, TimeUnit.SECONDS,new ArrayBlockingQueue<Runnable>(QUEUE_SIZE));while(true) {SenderTask st = new SenderTask();executor.submit(st);}}

    public void execute(Runnable command) {if (command == null)throw new NullPointerException();/** Proceed in 3 steps:** 1. If fewer than corePoolSize threads are running, try to* start a new thread with the given command as its first* task.  The call to addWorker atomically checks runState and* workerCount, and so prevents false alarms that would add* threads when it shouldn't, by returning false.** 2. If a task can be successfully queued, then we still need* to double-check whether we should have added a thread* (because existing ones died since last checking) or that* the pool shut down since entry into this method. So we* recheck state and if necessary roll back the enqueuing if* stopped, or start a new thread if there are none.** 3. If we cannot queue task, then we try to add a new* thread.  If it fails, we know we are shut down or saturated* and so reject the task.*/int c = ctl.get();if (workerCountOf(c) < corePoolSize) {if (addWorker(command, true))return;c = ctl.get();}if (isRunning(c) && workQueue.offer(command)) {int recheck = ctl.get();if (! isRunning(recheck) && remove(command))reject(command);else if (workerCountOf(recheck) == 0)addWorker(null, false);}else if (!addWorker(command, false))reject(command);}

 public class RejectedExecutionExceptionExample {public static void main(String[] args) {ExecutorService executor = new ThreadPoolExecutor(3, 3, 0L, TimeUnit.MILLISECONDS, new ArrayBlockingQueue<Runnable>(15));Worker tasks[] = new Worker[20];for(int i=0; i<20; i++){tasks[i] = new Worker(i);executor.execute(tasks[i]);}executor.shutdown();     executor.execute(tasks[0]);//继续执行任务}
}