Java中的 Threadpoolexecutor类

    /**
     * Executes the given task sometime in the future.  The task
     * may execute in a new thread or in an existing pooled thread.
     *
     * If the task cannot be submitted for execution, either because this
     * executor has been shutdown or because its capacity has been reached,
     * the task is handled by the current {@code RejectedExecutionHandler}.
     *
     * @param command the task to execute
     * @throws RejectedExecutionException at discretion of
     *         {@code RejectedExecutionHandler}, if the task
     *         cannot be accepted for execution
     * @throws NullPointerException if {@code command} is null
     */
    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);
    }

    /**
     * A handler for rejected tasks that throws a
     * {@code RejectedExecutionException}.
     */
    public static class AbortPolicy implements RejectedExecutionHandler {
        /**
         * Creates an {@code AbortPolicy}.
         */
        public AbortPolicy() { }

        /**
         * Always throws RejectedExecutionException.
         *
         * @param r the runnable task requested to be executed
         * @param e the executor attempting to execute this task
         * @throws RejectedExecutionException always
         */
        public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
            throw new RejectedExecutionException("Task " + r.toString() +
                                                 " rejected from " +
                                                 e.toString());
        }
    }

        ThreadPoolExecutor ex = new ThreadPoolExecutor(10, 100, 100L, TimeUnit.SECONDS, new LinkedBlockingQueue<>(10), new MyRejectPolicy());


    	private static class MyRejectPolicy implements RejectedExecutionHandler {

        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
            System.out.println("reject me,555");
            // send email ...
        }
    }

    protected void beforeExecute(Thread t, Runnable r) { }
    
    protected void afterExecute(Runnable r, Throwable t) { }

    protected void terminated() { }

    private static class  MyExecutor extends ThreadPoolExecutor{


        public MyExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) {
            super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);
        }

        @Override
        protected void beforeExecute(Thread t, Runnable r) {
            System.out.println("before");
        }

        @Override
        protected void afterExecute(Runnable r, Throwable t) {
            System.out.println("after");
        }

        @Override
        protected void terminated() {
            System.out.println("executor terminate");

        }
    }

    public static void main(String[] args) {
        ThreadPoolExecutor ex = new MyExecutor(10, 100, 100L, TimeUnit.SECONDS, new LinkedBlockingQueue<>(10), new MyRejectPolicy());
        ex.execute(()->{
            for (int i = 0; i < 10; ++i) {
                System.out.println("i:" + i);
            }
        });

        ex.execute(()->{
            for (int i = 0; i < 10; ++i) {
                System.out.println("j:" + i);
            }
        });

        ex.shutdown();
    }

before
i:0
i:1
i:2
i:3
i:4
i:5
before
i:6
i:7
i:8
i:9
j:0
j:1
j:2
j:3
j:4
j:5
j:6
j:7
after
j:8
j:9
after
executor terminate