实现callable接口-多线程下载图片

实现callable接口-多线程下载图片

说是了解即可，但在项目中还是遇到了，要掌握

实现步骤

1. 实现Callable接口
2. 重写call方法
3. 创建目标对象 Xxxxx t1 = new Xxxxxx();
4. 创建执行任务 ExecutorService ser = Executors.newFixedThreadPool(1);
5. 提交执行 Future result1 = ser.submit(t1);
6. 获取结果: boolean r1 = result1.get()
7. 关闭服务：ser.shutdownNow()

代码

package com.example.multi_thread;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

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() throws Exception {
        WebDownloader1 webDownloader1 = new WebDownloader1();
        webDownloader1.download(url, name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        TestCallable t1 = new TestCallable("https://www.baidu.com/img/PCtm_d9c8750bed0b3c7d089fa7d55720d6cf.png", "D:\\old_drive_F\\项目\\2021\\demo_kunag\\src\\main\\java\\com\\example\\multi_thread\\1.jpg");
        TestCallable t2 = new TestCallable("https://www.baidu.com/img/PCtm_d9c8750bed0b3c7d089fa7d55720d6cf.png", "D:\\old_drive_F\\项目\\2021\\demo_kunag\\src\\main\\java\\com\\example\\multi_thread\\2.jpg");
        TestCallable t3 = new TestCallable("https://www.baidu.com/img/PCtm_d9c8750bed0b3c7d089fa7d55720d6cf.png", "D:\\old_drive_F\\项目\\2021\\demo_kunag\\src\\main\\java\\com\\example\\multi_thread\\3.jpg");

        //1. 创建执行任务
        ExecutorService ser = Executors.newFixedThreadPool(3);
        //2. 提交执行
        Future<Boolean> result1 = ser.submit(t1);
        Future<Boolean> result2 = ser.submit(t2);
        Future<Boolean> result3 = ser.submit(t3);
        //3. 获取结果:
        boolean r1 = result1.get();
        boolean r2 = result2.get();
        boolean r3 = result3.get();
        //4. 关闭服务：
        ser.shutdownNow();

        System.out.println(r1);
        System.out.println(r2);
        System.out.println(r3);
    }

}

class WebDownloader1 {
    public void download(String url, String name) throws IOException {
        FileUtils.copyURLToFile(new URL(url), new File(name));
    }

}

结果

true
true
true