Java中的ThreadPoolExecutor线程池原理细节解析

public void execute(Runnable command) {
    if (command == null)
        throw new NullPointerException();
    int c = ctl.get();
    //判断工作线程数是否小于核心线程数
    if (workerCountOf(c) < corePoolSize) {
    	//是，创建一个新线程
        if (addWorker(command, true))
            return;
        c = ctl.get();
    }
    //否，将任务尝试添加到阻塞队列中，如果队列满了则会添加失败。
    if (isRunning(c) && workQueue.offer(command)) {
        int recheck = ctl.get();
        //判断线程池状态是否在运行中，不在运行中时，删除该任务
        if (! isRunning(recheck) && remove(command))
        	//不在运行中时，执行拒绝策略
            reject(command);
        //判断工作线程数是否为0
        else if (workerCountOf(recheck) == 0)
        	//为0的场合，尝试创建新线程
            addWorker(null, false);
    }
    //添加失败的场合，尝试创建一个新线程
    else if (!addWorker(command, false))
    	//如果添加失败，执行拒绝策略
        reject(command);
}

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

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