實現Callable介面(瞭解即可)

1. 實現Callable介面，需要返回值型別
2. 重寫call方法，需要丟擲異常
3. 建立目標物件
4. 建立執行服務:ExecutorService ser = Executors.newFixedThreadPool(1);
5. 提交執行：Future result1 = ser.submit(t1);
6. 獲取結果：boolean r1 = result1.get()
7. 關閉服務：ser.shutdownNow();

演示：利用callable改造下載圖片案例

import org.apache.commons.io.FileUtils;

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


//執行緒建立方式三：實現callable介面
/*
callable的好處
1.可以定義返回值
2.可以丟擲異常
 */
public class TestCallable implements Callable<Boolean> {
    private String url; //網路圖片地址
    private String name; //儲存的檔名

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

    //下載圖片執行緒的執行體
    @Override
    public Boolean call() {
        WebDownloader webDownloader = new WebDownloader();
        webDownloader.downloader(url,name);
        System.out.println("下載了檔名為："+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. 建立執行服務:
        ExecutorService ser = Executors.newFixedThreadPool(3);
        //2. 提交執行：
        Future<Boolean> r1 = ser.submit(t1);
        Future<Boolean> r2 = ser.submit(t2);
        Future<Boolean> r3 = ser.submit(t3);
        //3. 獲取結果：
        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. 關閉服務：
        ser.shutdownNow();
    }
}

//下載器 工具類
class WebDownloader {
    //下載方法
    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異常，downloader方法出現問題");
        }
    }
}