Java中的线程池共有几种？#

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public static ExecutorService newCachedThreadPool() {
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    // 这个线程池corePoolSize为0，maximumPoolSize为Integer.MAX_VALUE
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    // 意思也就是说来一个任务就创建一个woker，回收时间是60s
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    return new ThreadPoolExecutor(0, Integer.MAX_VALUE,
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                                60L, TimeUnit.SECONDS,
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                                new SynchronousQueue<Runnable>());
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}

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public static ExecutorService newFixedThreadPool(int nThreads, ThreadFactory threadFactory) {
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    // corePoolSize跟maximumPoolSize值一样，同时传入一个无界阻塞队列
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    // 该线程池的线程会维持在指定线程数，不会进行回收
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    return new ThreadPoolExecutor(nThreads, nThreads,
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                                0L, TimeUnit.MILLISECONDS,
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                                new LinkedBlockingQueue<Runnable>(),
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                                threadFactory);
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}

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public static ExecutorService newSingleThreadExecutor() {
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    // 线程池中只有一个线程进行任务执行，其他的都放入阻塞队列
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    // 外面包装的FinalizableDelegatedExecutorService类实现了finalize方法，在JVM垃圾回收的时候会关闭线程池
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    return new FinalizableDelegatedExecutorService
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        (new ThreadPoolExecutor(1, 1,
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                                0L, TimeUnit.MILLISECONDS,
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                                new LinkedBlockingQueue<Runnable>()));
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}

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public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {
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    return new ScheduledThreadPoolExecutor(corePoolSize);
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}