面试问题Executors有哪些创建线程池的方法

下面四个方法本质上都是调用ThreadPoolExecutor的构造方法：

1：Executors.newSingleThreadExecutor()

2：Executors.newFixedThreadPool(nThreads)

3：Executors.newCachedThreadPool()

4：Executors.newScheduledThreadPool(corePoolSize)

corePoolSize：线程池中保留的线程数量，即使这些线程是处于空闲状态

maximumPoolSize：线程池中可创建的最大线程数量

keepAliveTime：当线程数大于corePoolSize数量时，如果线程空闲，这个线程在这个空闲时间后将会销毁

unit：keepAliveTime时间单位

workQueue：任务队列

1：Executors.newSingleThreadExecutor()创建单线程任务线程池

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1. public static ExecutorService newSingleThreadExecutor() {  
2.         return new FinalizableDelegatedExecutorService  
3.             (new ThreadPoolExecutor(1, 1,  
4.                                     0L, TimeUnit.MILLISECONDS,  
5.                                     new LinkedBlockingQueue<Runnable>()));  
6.     }  

2：Executors.newFixedThreadPool(nThreads)创建固定数量线程线程池

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1. public static ExecutorService newFixedThreadPool(int nThreads) {  
2.        return new ThreadPoolExecutor(nThreads, nThreads,  
3.                                      0L, TimeUnit.MILLISECONDS,  
4.                                      new LinkedBlockingQueue<Runnable>());  
5.    }  

3：Executors.newCachedThreadPool()创建以默认60秒为空闲时间的缓存线程池，核心线程数为0

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1. public static ExecutorService newCachedThreadPool() {  
2.         return new ThreadPoolExecutor(0, Integer.MAX_VALUE,  
3.                                       60L, TimeUnit.SECONDS,  
4.                                       new SynchronousQueue<Runnable>());  
5.     }  

4：Executors.newScheduledThreadPool(corePoolSize)创建可以控制执行时间的线程池

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1. public static ScheduledExecutorService newScheduledThreadPool(int corePoolSize) {  
2.         return new ScheduledThreadPoolExecutor(corePoolSize);  
3.     }  

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1. public ScheduledThreadPoolExecutor(int corePoolSize) {  
2.        super(corePoolSize, Integer.MAX_VALUE, 0, NANOSECONDS,  
3.              new DelayedWorkQueue());  
4.    }