多线程编程之Runnable与Callable区别

Runnable

@FunctionalInterface     public interface Runnable {         /**          * When an object implementing interface <code>Runnable</code> is used          * to create a thread, starting the thread causes the object's          * <code>run</code> method to be called in that separately executing          * thread.          * <p>          * The general contract of the method <code>run</code> is that it may          * take any action whatsoever.          *          * @see     java.lang.Thread#run()          */         public abstract void run();     }           

Callable

@FunctionalInterface     public interface Callable<V> {         /**          * Computes a result, or throws an exception if unable to do so.          *          * @return computed result          * @throws Exception if unable to compute a result          */         V call() throws Exception;     }           

相同点：

1.都是接口，都能够实现多线程编程，都需要Thread.start()来启动线程。

不同点：

1.Callable接口支持返回执行结果，此时需要调用FutureTask.get()方法实现，此方法会阻塞主线程直到获取‘将来’结果；当不调用此方法时，主线程不会阻塞！

Callable使用

/**      * CallableImpl 简要描述      * <p> TODO:描述该类职责 </p>      *      * @author ckmike      * @version 1.0      * @date 18-12-6 下午8:53      * @copyright ckmike      **/     public class CallableImpl implements Callable<String> {         private String accept;         public CallableImpl(String accept) {             this.accept = accept;         }         @Override         public String call() throws Exception {             // 休眠             TimeUnit.SECONDS.sleep(3);             return this.accept;         }         public static void main(String[] args) throws ExecutionException, InterruptedException {             Callable<String> callable = new CallableImpl("my callable test!");             FutureTask<String> task = new FutureTask<>(callable);             long beginTime = System.currentTimeMillis();             // 创建线程             new Thread(task).start();             // 调用get()阻塞主线程，反之，线程不会阻塞             String result = task.get();             long endTime = System.currentTimeMillis();             System.out.println("hello : " + result);             System.out.println("cast : " + (endTime - beginTime) / 1000 + " second!");         }     }           

Runnable使用

/**      * RunnableImpl 简要描述      * <p> TODO:描述该类职责 </p>      *      * @author ckmike      * @version 1.0      * @date 18-12-6 下午9:03      * @copyright ckmike      **/     public class RunnableImpl implements Runnable {         public RunnableImpl(String accept) {             this.accept = accept;         }         private String accept;         @Override         public void run() {             // 线程阻塞 1 秒，此时有异常产生，只能在方法内部消化，无法上抛             try {                 TimeUnit.SECONDS.sleep(1);             } catch (InterruptedException e) {                 e.printStackTrace();             }             // 最终处理结果无法返回             System.out.println("hello : " + this.accept);         }         public static void main(String[] args) {             Runnable runnable = new RunnableImpl("my runable test!");             long beginTime = System.currentTimeMillis();             new Thread(runnable).start();             long endTime = System.currentTimeMillis();             System.out.println("cast : " + (endTime - beginTime) / 1000 + " second!");         }     }           

写这篇文章的原因是：面试时问道Runnable与Callable的区别，平时也就用Runnable比较多，基本上没有用过Callable，所以就挂了，哈哈哈，也总结给有需要的朋友。有知道Callable接口的使用场景吗？有的话可以留意分享给我吗？谢谢了！