JAVA线程池原理实例详解

public ThreadPoolExecutor(int corePoolSize,
               int maximumPoolSize,
               long keepAliveTime,
               TimeUnit unit,
               BlockingQueue workQueue,
               RejectedExecutionHandler handler) 

public void execute(Runnable command) {
    if (command == null)
      throw new NullPointerException(); //如果线程数大于等于基本线程数或者线程创建失败，将任务加入队列
    if (poolSize >= corePoolSize || !addIfUnderCorePoolSize(command)) {//线程池处于运行状态并且加入队列成功
      if (runState == RUNNING && workQueue.offer(command)) {
        if (runState != RUNNING || poolSize == 0)
          ensureQueuedTaskHandled(command);
      }//线程池不处于运行状态或者加入队列失败，则创建线程（创建的是非核心线程）
      else if (!addIfUnderMaximumPoolSize(command))//创建线程失败，则采取阻塞处理的方式
        reject(command); // is shutdown or saturated
    }
}

private boolean addIfUnderCorePoolSize(Runnable firstTask) {
    Thread t = null;
    final ReentrantLock mainLock = this.mainLock;
    mainLock.lock();
    try {
      if (poolSize 

private Thread addThread(Runnable firstTask) {
    Worker w = new Worker(firstTask);
    Thread t = threadFactory.newThread(w);
    if (t != null) {
      w.thread = t;
      workers.add(w);
      int nt = ++poolSize;
      if (nt > largestPoolSize)
        largestPoolSize = nt;
    }
    return t;
}

public void run() {
  try {
    Runnable task = firstTask;
    firstTask = null;
    while (task != null || (task = getTask()) != null) {
      runTask(task);
      task = null;
    }
  } finally {
    workerDone(this);
  }
}

public class ThreadPoolTest implements Runnable
{
  @Override
  public void run()
  {
    try
    {
      Thread.sleep(300);
    }
    catch (InterruptedException e)
    {
      e.printStackTrace();
    }
  }
}

public static void main(String[] args)
{
    LinkedBlockingQueue queue =
      new LinkedBlockingQueue(5);
    ThreadPoolExecutor threadPool = new ThreadPoolExecutor(5, 10, 60, TimeUnit.SECONDS, queue);
    for (int i = 0; i <16 ; i++)
    {
      threadPool.execute(
        new Thread(new ThreadPoolTest(), "Thread".concat(i + "")));
      System.out.println("线程池中活跃的线程数： " + threadPool.getPoolSize());
      if (queue.size() > 0)
      {
        System.out.println("----------------队列中阻塞的线程数" + queue.size());
      }
    }
    threadPool.shutdown();
}

public static void main(String[] args)
{
    LinkedBlockingQueue queue =
      new LinkedBlockingQueue(3);
    RejectedExecutionHandler handler = new ThreadPoolExecutor.DiscardPolicy();
    ThreadPoolExecutor threadPool = new ThreadPoolExecutor(2, 5, 60, TimeUnit.SECONDS, queue,handler);
    for (int i = 0; i <9 ; i++)
    {
      threadPool.execute(
        new Thread(new ThreadPoolTest(), "Thread".concat(i + "")));
      System.out.println("线程池中活跃的线程数： " + threadPool.getPoolSize());
      if (queue.size() > 0)
      {
        System.out.println("----------------队列中阻塞的线程数" + queue.size());
      }
    }
    threadPool.shutdown();
}

RejectedExecutionHandler handler = new ThreadPoolExecutor.DiscardPolicy();
ThreadPoolExecutor threadPool = new ThreadPoolExecutor(2, 5, 60, TimeUnit.SECONDS, queue,handler);

ThreadPoolExecutor threadPool = new ThreadPoolExecutor(2, 5, 60, TimeUnit.SECONDS, queue);
threadPool.setRejectedExecutionHandler(new ThreadPoolExecutor.AbortPolicy());