JDK 中ExecutorService建立线程池

下面给出了一个网络服务的简单结构，这里线程池中的线程做为传入的请求。它使用了预先配置的 Executors.newFixedThreadPool(int) 工厂方法：

class NetworkService implements Runnable {
    private final ServerSocket serverSocket;
    private final ExecutorService pool;

    public NetworkService(int port, int poolSize)
        throws IOException {
      serverSocket = new ServerSocket(port);
      pool = Executors.newFixedThreadPool(poolSize);
    }
 
    public void run() { // run the service
      try {
        for (;;) {
          pool.execute(new Handler(serverSocket.accept()));
        }
      } catch (IOException ex) {
        pool.shutdown();
      }
    }
  }

  class Handler implements Runnable {
    private final Socket socket;
    Handler(Socket socket) { this.socket = socket; }
    public void run() {
      // read and service request on socket
    }
 }

下列方法分两个阶段关闭ExecutorService。第一阶段调用shutdown拒绝传入任务，而后调用shutdownNow（若有必要）取消全部遗留的任务：

void shutdownAndAwaitTermination(ExecutorService pool) {
   pool.shutdown(); // Disable new tasks from being submitted
   try {
     // Wait a while for existing tasks to terminate
     if (!pool.awaitTermination(60, TimeUnit.SECONDS)) {
       pool.shutdownNow(); // Cancel currently executing tasks
       // Wait a while for tasks to respond to being cancelled
       if (!pool.awaitTermination(60, TimeUnit.SECONDS))
           System.err.println("Pool did not terminate");
     }
   } catch (InterruptedException ie) {
     // (Re-)Cancel if current thread also interrupted
     pool.shutdownNow();
     // Preserve interrupt status
     Thread.currentThread().interrupt();
   }
 }

内存一致性效果：线程中向ExecutorService提交Runnable或Callable任务以前的操做 happen-before 由该任务所提取的全部操做，后者依次 happen-before 经过Future.get()获取的结果。