线程创建

1. Thread：继承Thread类（重点）
2. Runnable：实现Runnable接口（重点）
3. Callable：实现Callable接口（了解）

继承Thread类

• 自定义线程类继承 Thread类
• 重写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

// 重写run()方法, alt+insert快捷键
public class StartThread1 extends Thread{
    // 线程入口点
    @Override
    public void run() {
        // 线程体
        for (int i = 0; i < 20; i++) {
            System.out.println("多线程");
        }
    }
}

// 调用start()方法启动线程
public class MainThread    {
    public static void main(String[] args) {
        // 创建线程对象
        StartThread1 th1 = new StartThread1();
        th1.start();
        // start 启用后和底下代码交替执行
        for (int i = 0; i < 2000; i++) {
            System.out.println("main方法");
        }
    }
}

• 下载图片

线程开启不一定立即执行，需要看CPU的调度

import org.apache.commons.io.FileUtils;

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

public class PicThread extends Thread {
    private String url = ""; // 网络图片地址
    private String name = ""; // 保存路径

    // 构造器，初始化地址
    public PicThread(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("路径"+name);
    }

    // 启动线程
    public static void main(String[] args) {
        String url = "https://img0.bdstatic.com/static/searchdetail/img/logo-2X_2dd9a28.png";
        String name = "C:\\Users\\Jie7\\IdeaProjects\\Test\\src\\baidulogo";
        // 多线程,启动，无序
        PicThread picThread1 = new PicThread(url, name +"1.png");
        PicThread picThread2 = new PicThread(url, name +"2.png");
        PicThread picThread3 = new PicThread(url, name +"3.png");
        picThread1.start();
        picThread2.start();
        picThread3.start();


    }
}

class WebDownloader {
    // 远程下载
    // 远程路径，存储地址+名字
    public void downloader(String url, String name) {
        try {
            FileUtils.copyURLToFile(new URL(url), new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("文件下载失败");
        }
    }
}