多线程之线程创建-优快云博客

本文链接：https://blog.youkuaiyun.com/weixin_47587613/article/details/118294794

本文介绍了Java中创建和使用多线程的三种常见方法：继承Thread类、实现Runnable接口及Callable接口。通过具体实例展示了如何实现多线程下载图片、模拟龟兔赛跑等场景，并探讨了线程安全性问题。

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线程创建

继承Thread类

package com.yeyue.demo01;

//创建线程方式一：继承Thread类，重写run（）方法，调用start开启线程

//线程开始不一定立即执行，由cpu调度

public class TestThread1 extends Thread {
    @Override
    public void run() {
        //run方法线程体
        for (int i = 0; i < 20; i++) {
            System.out.println("我在看代码---"+i);
        }
    }

    public static void main(String[] args) {
        //main 线程，主线程

        //创建一个线程对象
        TestThread1 testThread1 = new TestThread1();

        //调用start（）方法开启线程
        testThread1.start();

        for (int i = 0; i < 100; i++) {
            System.out.println("我在学习多线程----" + i);
        }
    }
}

实现Runnable接口

多线程下载图片

package com.yeyue.demo01;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;

//练习Thread，实现多线程同步下载图片
public class TestThread2 implements Runnable {
    private String url; //图片下载的url
    private String name; //下载的图片保存的图片名字


    public TestThread2(String url,String name){
        this.url = url;
        this.name = name;
    }

    //下载图片的执行体
    @Override
    public void run() {
        WebDownloader webDownloader = new WebDownloader();
        webDownloader.downloader(url,name);
        System.out.println("下载了文件名：" + name);
    }

    public static void main(String[] args) {
        TestThread2 t1 = new TestThread2("https://img2.baidu.com/it/u=2253502056,189588800&fm=26&fmt=auto&gp=0.jpg","1.jpg");
        TestThread2 t2 = new TestThread2("https://img2.baidu.com/it/u=3529414605,308711291&fm=26&fmt=auto&gp=0.jpg","2.jpg");
        TestThread2 t3 = new TestThread2("https://img1.baidu.com/it/u=1863405005,3705892836&fm=26&fmt=auto&gp=0.jpg","3.jpg");

        new Thread(t1).start();
        new Thread(t2).start();
        new Thread(t3).start();

    }

}

//下载器
class WebDownloader{
    //下载方法
    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方法出现问题");
        }
    }
}

买票

package com.yeyue.demo01;

//多个线程同时操作一个对象
//买火车票的例子

//多个线程操作同一个资源的情况下，资源不安全了
public class TestThread4 implements Runnable {

    //票数
    private int ticketNums =10;

    @Override
    public void run() {
        while (true){
            if(ticketNums <= 0){
                break;
            }
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+"-->拿到了第"+ticketNums--+"票");
        }
    }

    public static void main(String[] args) {
        TestThread4 ticket = new TestThread4();

        new Thread(ticket,"小明").start();
        new Thread(ticket,"老师").start();
        new Thread(ticket,"黄牛党").start();
    }
}

实现Callable接口

package com.yeyue.demo01;

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; //图片下载的url
    private String name; //下载的图片保存的图片名字


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

    //下载图片的执行体
    @Override
    public Boolean call() {
        WebDownloader1 webDownloader1 = new WebDownloader1();
        webDownloader1.downloader1(url,name);
        System.out.println("下载了文件名：" + name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        TestCallable t1 = new TestCallable("https://img2.baidu.com/it/u=2253502056,189588800&fm=26&fmt=auto&gp=0.jpg","1.jpg");
        TestCallable t2 = new TestCallable("https://img2.baidu.com/it/u=3529414605,308711291&fm=26&fmt=auto&gp=0.jpg","2.jpg");
        TestCallable t3 = new TestCallable("https://img1.baidu.com/it/u=1863405005,3705892836&fm=26&fmt=auto&gp=0.jpg","3.jpg");

        //创建执行服务
        ExecutorService ser = (ExecutorService) Executors.newFixedThreadPool(3);

        //提交执行：
        Future<Boolean> r1 = ser.submit(t1);
        Future<Boolean> r2 = ser.submit(t2);
        Future<Boolean> r3 = ser.submit(t3);

        //获取结果
        boolean rs1 = r1.get();
        boolean rs2 = r2.get();
        boolean rs3 = r3.get();

        System.out.println(rs1);
        System.out.println(rs2);
        System.out.println(rs3);

        //关闭服务
        ser.shutdownNow();
    }

}

//下载器
class WebDownloader1 {
    //下载方法
    public void downloader1(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方法出现问题");
        }
    }
}

模拟龟兔赛跑

package com.yeyue.demo01;

//模拟龟兔赛跑
public class Race implements Runnable{

    private static String winner;

    @Override
    public void run() {
        for (int i = 0; i <= 100; i++) {

            if(Thread.currentThread().getName().equals("兔子") && i%10==0){
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            //判断游戏是否结束
            boolean flag = gameOver(i);
            if(flag){
                break;
            }


            System.out.println(Thread.currentThread().getName()+"跑了"+i+"步");
        }
    }

    private boolean gameOver(int steps){
        if(winner!=null){
            return true;
        }{
            if(steps>=100){
                winner = Thread.currentThread().getName();
                System.out.println("winner is " + 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();
    }

}