Callable接口:
public interface Callable<V> { V call() throws Exception; }
Runnable接口:
public interface Runnable { public abstract void run(); }
相同点:
- 两者都是接口;(废话)
- 两者都可用来编写多线程程序;
- 两者都需要调用Thread.start()启动线程;
不同点:
- 两者最大的不同点是:实现Callable接口的任务线程能返回执行结果;而实现Runnable接口的任务线程不能返回结果;
- Callable接口的call()方法允许抛出异常;而Runnable接口的run()方法的异常只能在内部消化,不能继续上抛;
注意点:
- 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工作的Demo:
package com.callable.runnable; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.FutureTask; /** * Created on 2016/5/18. */ public class CallableImpl implements Callable<String> { public CallableImpl(String acceptStr) { this.acceptStr = acceptStr; } private String acceptStr; @Override public String call() throws Exception { // 任务阻塞 1 秒 Thread.sleep(1000); return this.acceptStr + " append some chars and return it!"; } 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!"); } }
测试结果:
hello : my callable test! append some chars and return it! cast : 1 second! Process finished with exit code 0