详见：http://blog.yemou.net/article/query/info/tytfjhfascvhzxcyt125
毫无疑问 Runnable会进行异步执行，此处不多说，主要说明Callable的使用，看实例：
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public class ThreadTest { public static void main(String[] args) throws InterruptedException, ExecutionException { ExecutorService executor = Executors.newFixedThreadPool(4); MyTread m1 = new MyTread(); Future f = executor.submit(m1); // System.out.println(f.get()); executor.shutdown(); System.out.println("主线程执行完了"); } } |
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class MyTread implements Callable<String> { @Override public String call() { try { System.out.println("线程调度：" + Thread.currentThread()); TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); } return "123"; }} |
此程序虽然获取了call方法的返回值，但是没有做处理，所以主线程main和m1同时执行，执行结果如下：
主线程执行完了
线程调度：Thread[pool-1-thread-1,5,main]
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public class ThreadTest { public static void main(String[] args) throws InterruptedException, ExecutionException { ExecutorService executor = Executors.newFixedThreadPool(4); MyTread m1 = new MyTread(); Future f = executor.submit(m1); System.out.println(f.get()); // 进行了输出 executor.shutdown(); System.out.println("主线程执行完了"); } } |
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class MyTread implements Callable<String> { @Override public String call() { try { System.out.println("线程调度：" + Thread.currentThread()); TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); } return "123"; }} |
在2中，对m1中call方法的返回值在main中进行了处理（输出），所以在此种情况下，main需要等待m1执行完，再继续执行，执行结果如下
线程调度：Thread[pool-1-thread-1,5,main]
123
主线程执行完了
3、再看当主线程中同时启动两个由Callable生成的线程时
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public class ThreadTest { public static void main(String[] args) throws InterruptedException, ExecutionException { ExecutorService executor = Executors.newFixedThreadPool(4); MyTread m1 = new MyTread(); MyTread2 m2 = new MyTread2(); Long time1 = TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis()); Future f = executor.submit(m1); Future f2 = executor.submit(m2); System.out.println(f.get()); // 进行了输出m1 System.out.println(f2.get()); // 进行了输出m2 executor.shutdown(); System.out.println("主线程执行完了"); Long time2 = TimeUnit.MILLISECONDS.toSeconds(System.currentTimeMillis()); System.out.println("主线程等待了" + (time2 - time1) + "秒"); } } |
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class MyTread implements Callable<String> { @Override public String call() { try { System.out.println("线程调度：" + Thread.currentThread()); TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); } return "123"; }} class MyTread2 implements Callable<String> { @Override public String call() { try { System.out.println("线程调度2：" + Thread.currentThread()); TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); } return "abc"; }} |
当不对m1和m2做输出时，main和m1、m2并发执行，当对m1和m2中任意一个的返回值进行处理的时候，main需要等待，但是m1和m2之前仍然是并发执行，执行结果如下：
线程调度2：Thread[pool-1-thread-2,5,main]
线程调度：Thread[pool-1-thread-1,5,main]
123
abc
主线程执行完了
主线程等待了3秒