1、对比几种线程池的创建

public static ExecutorService newCachedThreadPool() {
        return new ThreadPoolExecutor(0, Integer.MAX_VALUE,60L, TimeUnit.SECONDS,new SynchronousQueue<Runnable>());
}

public static ScheduledExecutorService newSingleThreadScheduledExecutor() {
    return new DelegatedScheduledExecutorService(new ScheduledThreadPoolExecutor(1));
}

/**SingleThreadExecutor、FixedThreadPool允许的请求队列的长度为Integer.MAX_VALUE(LinkedBlockingQueue初始化的时候默认容量为Integer.MAX_VALUE)，这样容易堆积大量的请求，导致OOM**/
public static ExecutorService newFixedThreadPool(int nThreads) {
        return new ThreadPoolExecutor(nThreads, nThreads,0L, TimeUnit.MILLISECONDS,new LinkedBlockingQueue<Runnable>());
}

public static ExecutorService newSingleThreadExecutor() {
        return new FinalizableDelegatedExecutorService (new ThreadPoolExecutor(1, 1,  0L, TimeUnit.MILLISECONDS,
                                    new LinkedBlockingQueue<Runnable>()));
}

public static ExecutorService newWorkStealingPool() {
        return new ForkJoinPool(Runtime.getRuntime().availableProcessors(), ForkJoinPool.defaultForkJoinWorkerThreadFactory,
             null, true);
}

public static ExecutorService unconfigurableExecutorService(ExecutorService executor) {
        if (executor == null)
            throw new NullPointerException();
        return new DelegatedExecutorService(executor);
    }

结论：有一大半线程池内部的实现都是ThreadPoolExecutor。