创建线程

继承Thread类

• Thread
  1. 自定义线程类继承 Thread类
  2. 重写 run() 方法，编写线程执行体。
  3. 创建线程对象，调用 start() 方法启动线程。
• 总结：线程开启不一定立即执行，由cpu统一调度执行

实现Runnable接口

• 定义一个类实现 Runnable 接口
• 实现 run() 方法，编写线程执行体
• 创建线程对象，调用 start() 方法启动线程
• 推荐使用Runnable对象，因为Java单继承的局限性

实现Callable接口

• 实现 Callable 接口，需要定义返回值类型
• 重写 call() 方法，需要抛出异常
• 创建Callable目标对象
• 创建执行服务: ExecutorService service = Executors.newFixedThreadPool(3);
• 提交执行: Future result1 = service.submit(t1);
• 获取结果: Boolean b1 = result1.get();
• 关闭服务: service.shutdownNow();
• 案例

package com.Thread;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.*;

public class TestCallable implements Callable<Boolean> {
    private String url;
    private String name;

    public TestCallable(String url, String name){
        this.url = url;
        this.name = name;
    }

    @Override
    public Boolean call() {
        WebDownLoader webDownLoader = new WebDownLoader();
        webDownLoader.downloader(url, name);
        System.out.println("下载了文件名为：" + name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        //创建Callable对象
        TestCallable t1 = new TestCallable("https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fb-ssl.duitang.com%2Fuploads%2Fitem%2F201311%2F28%2F20131128103655_uWKi4.thumb.700_0.jpeg&refer=http%3A%2F%2Fb-ssl.duitang.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1613575351&t=6c5683490ce7ff6518800f588535c520","1.jpg");
        TestCallable t2 = new TestCallable("https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fc-ssl.duitang.com%2Fuploads%2Fitem%2F201402%2F06%2F20140206212537_xkASi.thumb.400_0.jpeg&refer=http%3A%2F%2Fc-ssl.duitang.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1613575457&t=2ac899661bce8cfca45e005560149a84","2.jpg");
        TestCallable t3 = new TestCallable("https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fb-ssl.duitang.com%2Fuploads%2Fitem%2F201509%2F06%2F20150906220833_dFume.thumb.700_0.jpeg&refer=http%3A%2F%2Fb-ssl.duitang.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=jpeg?sec=1613575469&t=438a4cdb105e3f854a3933463c6e90bf","3.jpg");
        //创建执行服务
        ExecutorService service = Executors.newFixedThreadPool(3);
        //提交执行任务
        Future<Boolean> result1 = service.submit(t1);
        Future<Boolean> result2 = service.submit(t2);
        Future<Boolean> result3 = service.submit(t3);
        //获取执行结果
        Boolean b1 = result1.get();
        Boolean b2 = result2.get();
        Boolean b3 = result3.get();
        //关闭服务
        service.shutdownNow();
    }
}


class WebDownLoader1{
    public void downloader(String url, String name){
        try {
            FileUtils.copyURLToFile(new URL(url), new File(name));

        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("IO异常，downloader下载文件出错");
        }
    }
}

小结

• 继承Thread类
  1. 子类继承Thread类具备多线程能力
  2. 启动线程: 子类对象.start()
  3. ==不建议使用: 避免OOP单继承局限性==
• 实现Runnable接口
  1. 实现接口Runnable具有多线程能力
  2. 启动线程: 传入目标对象 + Thread对象.start()
  3. ==推荐使用: 避免单继承局限性，灵活方便，方便同一个对象被多个线程使用==

示例

• 龟兔赛跑

package com.Thread;

public class Race implements Runnable {
    private static String winner;

    @Override
    public void run() {
        //模拟赛道为100m
        for (int i = 1; i <= 100; i++) {
            //模拟兔子睡觉
            if (Thread.currentThread().getName().equals("兔子") && i%10 == 0 ){
                try {
                    //让当前线程睡多少毫秒
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            boolean flag = gameOver(i);
            if (flag){
                break;
            }
            System.out.println(Thread.currentThread().getName() + "----->跑了" + i + "米");
        }
    }

    //判断比赛是否完成
    private boolean gameOver(int steps){
        if (winner != null){
            return true;
        }
        if (steps >= 100){
            winner = Thread.currentThread().getName();
            System.out.println("胜利者是 " + winner);
            return true;
        }
        return false;
    }

    public static void main(String[] args) {
        Race race = new Race();

        new Thread(race, "兔子").start();
        new Thread(race, "乌龟").start();
    }
}