深入理解线程通信 (3)

如果是用线程池来管理线程，可以使用以下方式来让主线程等待线程池中所有任务执行完毕:

private static void executorService() throws Exception{ BlockingQueue<Runnable> queue = new LinkedBlockingQueue<>(10) ; ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(5,5,1, TimeUnit.MILLISECONDS,queue) ; poolExecutor.execute(new Runnable() { @Override public void run() { LOGGER.info("running"); try { Thread.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); } } }); poolExecutor.execute(new Runnable() { @Override public void run() { LOGGER.info("running2"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } } }); poolExecutor.shutdown(); while (!poolExecutor.awaitTermination(1,TimeUnit.SECONDS)){ LOGGER.info("线程还在执行。。。"); } LOGGER.info("main over"); }

输出结果:

2018-03-16 20:18:01.273 [pool-1-thread-2] INFO c.c.actual.ThreadCommunication - running2 2018-03-16 20:18:01.273 [pool-1-thread-1] INFO c.c.actual.ThreadCommunication - running 2018-03-16 20:18:02.273 [main] INFO c.c.actual.ThreadCommunication - 线程还在执行。。。 2018-03-16 20:18:03.278 [main] INFO c.c.actual.ThreadCommunication - 线程还在执行。。。 2018-03-16 20:18:04.278 [main] INFO c.c.actual.ThreadCommunication - main over

使用这个 awaitTermination() 方法的前提需要关闭线程池，如调用了 shutdown() 方法。

调用了 shutdown() 之后线程池会停止接受新任务，并且会平滑的关闭线程池中现有的任务。

管道通信 public static void piped() throws IOException { //面向于字符 PipedInputStream 面向于字节 PipedWriter writer = new PipedWriter(); PipedReader reader = new PipedReader(); //输入输出流建立连接 writer.connect(reader); Thread t1 = new Thread(new Runnable() { @Override public void run() { LOGGER.info("running"); try { for (int i = 0; i < 10; i++) { writer.write(i+""); Thread.sleep(10); } } catch (Exception e) { } finally { try { writer.close(); } catch (IOException e) { e.printStackTrace(); } } } }); Thread t2 = new Thread(new Runnable() { @Override public void run() { LOGGER.info("running2"); int msg = 0; try { while ((msg = reader.read()) != -1) { LOGGER.info("msg={}", (char) msg); } } catch (Exception e) { } } }); t1.start(); t2.start(); }

输出结果:

2018-03-16 19:56:43.014 [Thread-0] INFO c.c.actual.ThreadCommunication - running 2018-03-16 19:56:43.014 [Thread-1] INFO c.c.actual.ThreadCommunication - running2 2018-03-16 19:56:43.130 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=0 2018-03-16 19:56:43.132 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=1 2018-03-16 19:56:43.132 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=2 2018-03-16 19:56:43.133 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=3 2018-03-16 19:56:43.133 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=4 2018-03-16 19:56:43.133 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=5 2018-03-16 19:56:43.133 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=6 2018-03-16 19:56:43.134 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=7 2018-03-16 19:56:43.134 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=8 2018-03-16 19:56:43.134 [Thread-1] INFO c.c.actual.ThreadCommunication - msg=9

Java 虽说是基于内存通信的，但也可以使用管道通信。

需要注意的是，输入流和输出流需要首先建立连接。这样线程 B 就可以收到线程 A 发出的消息了。

实际开发中可以灵活根据需求选择最适合的线程通信方式。