实现Callable接口(了解即可)

实现Callable接口(了解即可)

1. 实现Callable接口，需要返回值类型
2. 重写call方法，需要抛出异常
3. 创建目标对象
4. 创建执行服务: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();

演示：利用callable改造下载图片案例

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import org.apache.commons.io.FileUtils;

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


//线程创建方式三：实现callable接口
/*
callable的好处
1.可以定义返回值
2.可以抛出异常
 */
public class TestCallable implements Callable<Boolean> {
    private String url; //网络图片地址
    private String name; //保存的文件名

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

    //下载图片线程的执行体
    @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 {
        TestCallable t1 = new TestCallable("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1594717080876&di=fe083e5f436c12d673004789fa9c9398&imgtype=0&src=http%3A%2F%2Fa3.att.hudong.com%2F14%2F75%2F01300000164186121366756803686.jpg","1.jpg");
        TestCallable t2 = new TestCallable("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1594717290398&di=e0c6f6d72e6678a887b672793129c24e&imgtype=0&src=http%3A%2F%2Fa0.att.hudong.com%2F56%2F12%2F01300000164151121576126282411.jpg","2.jpg");
        TestCallable t3 = new TestCallable("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1594717332850&di=63815e0cd3207db1c64dab607ecff742&imgtype=0&src=http%3A%2F%2Fa4.att.hudong.com%2F52%2F52%2F01200000169026136208529565374.jpg","3.jpg");

        //1. 创建执行服务:
        ExecutorService ser = Executors.newFixedThreadPool(3);
        //2. 提交执行：
        Future<Boolean> r1 = ser.submit(t1);
        Future<Boolean> r2 = ser.submit(t2);
        Future<Boolean> r3 = ser.submit(t3);
        //3. 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);
        //4. 关闭服务：
        ser.shutdownNow();
    }
}

//下载器 工具类
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");
        }
    }
}