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  • 说说Runnable与Callable

    Callable接口:

    public interface Callable<V> {
        V call() throws Exception;
    }

     Runnable接口:

    public interface Runnable {
        public abstract void run();
    }

     相同点:

    1. 两者都是接口;(废话)
    2. 两者都可用来编写多线程程序;
    3. 两者都需要调用Thread.start()启动线程;

     不同点:

    1. 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;
    2. 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:

    复制代码
    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!");
        }
    }
    复制代码

     测试结果:

    hello : my callable test! append some chars and return it!
    cast : 1 second!
    
    Process finished with exit code 0
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  • 原文地址:https://www.cnblogs.com/moxiaotao/p/9779493.html
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