Three ways to create multi-threaded daily notes

Three ways to create multi-threaded daily notes

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1. Inherit the Thread class, rewrite the run() method, and call start to start the thread

Summary: Thread start () may not be executed immediately. It is scheduled and executed by the CPU. Calling the run() method is executed immediately.
Reason: To call the run() method, the main thread first calls the run() method, and then executes the latter method, and then calls start. The () method is equivalent to starting two threads and executing alternately.

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Example: multiple threads download pictures at the same time

package com.zuoyan.lesson01;

import org.apache.commons.io.FileUtils;

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

/**
 * 多个线程同时下载图片
 */
public class ThreadDownFile extends Thread{
    
    

    //图片地址
    private String url;

    //文件名称
    private String name;

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

    @Override
    public void run() {
    
    
        WebDownLoader webDownLoader = new WebDownLoader();
        webDownLoader.downLoader(url, name);
        System.out.println("下载了文件名为：" + name);
    }

    public static void main(String[] args) {
    
    
        ThreadDownFile thread1 = new ThreadDownFile("http://www.kennerchina.cn/upload/show/68dfcf42-6c7a-4060-bc9e-deb4ad321c9e-banner.jpg", "1.jpg");
        ThreadDownFile thread2 = new ThreadDownFile("http://www.kennerchina.cn/upload/showPageConfig/50830201-bee8-4348-812e-c59dd31905d6-Sky2.jpg", "2.jpg");
        ThreadDownFile thread3 = new ThreadDownFile("http://www.kennerchina.cn/upload/showStyle/45082cd1-75d8-4a56-a1ec-9c16399f7964-kenner-70.png", "3.jpg");

        thread1.start();
        thread2.start();
        thread3.start();
    }

}

//下载器
class WebDownLoader {
    
    
    public void downLoader(String url, String name) {
    
    
        try {
    
    
            //下载
            FileUtils.copyURLToFile(new URL(url), new File(name));
        } catch (IOException e) {
    
    
            e.printStackTrace();
            System.out.println("IO异常，downLoader方法出错");
        }
    }
}

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2. Implement the Runnable interface and rewrite the run() method

When the thread is executed, throw into the runnable interface implementation class and call the start() method

package com.zuoyan.lesson01;

/**
 * 创建线程方式2：实现runnable接口，重写run()方法，执行线程时丢入runnable接口实现类，调用start()方法
 */
public class RunnableThread implements Runnable{
    
    

    @Override
    public void run() {
    
    
        for (int i = 0; i < 200; i++) {
    
    
            System.out.println("测试run()方法:" + i);
        }
    }

    public static void main(String[] args) {
    
    
        RunnableThread runnableThread = new RunnableThread();

        //创建线程对象，通过线程对象来开启线程，代理，调用start()方法
        new Thread(runnableThread).start();

        for (int i = 0; i < 200; i++) {
    
    
            System.out.println("主方法:" + i);
        }
    }
}

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3. Implement the Callable interface, rewrite the call method, and have a return value

package com.zuoyan.lesson01;

import org.apache.commons.io.FileUtils;

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

/**
 * 创建多线程方式三：实现Callable接口,重写call()方法
 */
public class CallableThread implements Callable<Boolean> {
    
    

    private String url;

    private String name;

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


    @Override
    public Boolean call() throws Exception {
    
    
        WebDownLoader2 webDownLoader = new WebDownLoader2();
        webDownLoader.downLoader(url, name);
        System.out.println("下载了文件：" + name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
    
    
        CallableThread t1 = new CallableThread("https://pics7.baidu.com/feed/adaf2edda3cc7cd97ab1d177f1e8cb38ba0e91f6.jpeg?token=0790121cb37f3897c85b66b702fad038&s=A832C614642000BA870E7E820300709C", "1.jpg");
        CallableThread t2 = new CallableThread("https://pics4.baidu.com/feed/f2deb48f8c5494ee8d49b8a086130af998257e0a.png?token=4cb1c7eb18cacf1b48120659b6256554&s=B123DC14C770418E1F5AF1490300F0B9", "2.jpg");
        CallableThread t3 = new CallableThread("https://pics3.baidu.com/feed/d1160924ab18972bb05edb52422b918e9f510a34.png?token=ad07ba0717cb7900ec8eafd0a0aeda8b&s=40085F320DDECCCE105061D9030050B2", "3.jpg");

        //创建服务执行(创建3个线程)
        ExecutorService service = Executors.newFixedThreadPool(3);

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

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

        //打印返回值结果
        System.out.println(rs1);
        System.out.println(rs2);
        System.out.println(rs3);

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


class WebDownLoader2{
    
    
    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");
        }
    }
}

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3. Summary

1. Inherit the Thread class
   : Subclasses inherit the Thread class with multi-threading capabilities
   : Start method: Subclass object.start()
   : Not recommended : Avoid the limitations of OOP single inheritance

2. Implement runnable interface
   : Implement interface runnable with multi-threading capability
   : Start thread: pass in the target object + Thread object. Start()
   : Recommended use : avoid the limitations of single inheritance, flexible and convenient, and convenient for one object to be used by multiple threads

3. Implement the Callable interface
   : You can define the return value
   : You can throw an exception