Java 多线程实现方式三：实现 Callable 接口

完整套路

java 通过实现Callable 接口来实现多线程相比较于继承Thread 接口和 实现Runnable 接口比较麻烦，但好处是可以有返回值。
基本套路：
1. 创建目标对象
2. 创建执行服务
3. 提交执行
4. 获取结果
5. 关闭服务
6.
继续方式一的下载图片，改写一下：

public class CDownload implements Callable<Boolean>{
    private String url;
    private String name;
    public CDownload(String url, String name) {
        this.url = url;
        this.name = name;
    }
    @Override
    public Boolean call() throws Exception {
        WebDownLoad wd = new WebDownLoad();
        wd.download(url, name);
        System.out.println(name);
        return true;
    }
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        CDownload td1 = new CDownload("http://img11.360buyimg.com/n1/s450x450_jfs/t1/95372/26/10103/109107/5e181892Eb698a3bc/2033bb2f00c38f93.jpg", "电脑.jpg");
        CDownload td2 = new CDownload("http://img14.360buyimg.com/n1/s450x450_jfs/t1/106229/22/9051/174570/5e0d4a59E099ec5cd/2501bf3e7f96c1fb.jpg", "键盘.jpg");
        CDownload td3 = new CDownload("http://img13.360buyimg.com/n1/s450x450_jfs/t1/5916/10/5128/160256/5b9f0e9bEbc9f4db4/14f062751af6ce26.jpg", "鼠标.jpg");
        // 创建执行服务
        ExecutorService ser =  Executors.newFixedThreadPool(3);
        // 提交执行
        Future<Boolean> r1 =  ser.submit(td1);
        Future<Boolean> r2 =  ser.submit(td2);
        Future<Boolean> r3 =  ser.submit(td3);
        // 获取结果
        Boolean ret1 = r1.get();
        Boolean ret2 = r2.get();
        Boolean ret3 = r3.get();
        System.out.println(ret1 + "--" + ret2 + "--" + ret3);
        // 关闭服务
        ser.shutdownNow();
    }

}

简单写法：

package com.xzlf.testThread;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class TestFutrueTask {
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        // 创建任务
        MyCall call = new MyCall();
        // 交给任务管理器
        FutureTask<String> task = new FutureTask<String>(call);
        // 创建代理类并启动线程
        new Thread(task).start();
        System.out.println("获取结果-->" + task.get());
        System.out.println("任务是否执行完成-->" + task.isDone());
    }
}


class MyCall implements Callable<String>{
    @Override
    public String call() throws Exception {
        String[] strs = new String[]{"java", "pyhton", "html", "orcal", "tomcat"};
        String result = strs[(int) (Math.random()*5)];
        return result;
    }
}