多線程程式設計之Runnable與Callable差別

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;     }           

相同點：

1.都是接口，都能夠實作多線程程式設計，都需要Thread.start()來啟動線程。

不同點：

1.Callable接口支援傳回執行結果，此時需要調用FutureTask.get()方法實作，此方法會阻塞主線程直到擷取‘将來’結果；當不調用此方法時，主線程不會阻塞！

Callable使用

/**      * CallableImpl 簡要描述      * <p> TODO:描述該類職責 </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();             // 建立線程             new Thread(task).start();             // 調用get()阻塞主線程，反之，線程不會阻塞             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 簡要描述      * <p> TODO:描述該類職責 </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() {             // 線程阻塞 1 秒，此時有異常産生，隻能在方法内部消化，無法上抛             try {                 TimeUnit.SECONDS.sleep(1);             } catch (InterruptedException e) {                 e.printStackTrace();             }             // 最終處理結果無法傳回             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!");         }     }           

寫這篇文章的原因是：面試時問道Runnable與Callable的差別，平時也就用Runnable比較多，基本上沒有用過Callable，是以就挂了，哈哈哈，也總結給有需要的朋友。有知道Callable接口的使用場景嗎？有的話可以留意分享給我嗎？謝謝了！