求帮助 这个怎么改？求有条件的来说说

package com.cskaoyan._27day;

import java.util.concurrent.*;

public class _7Exercise implements Callable {

// 定义
public String name;
public String url;

public _7Exercise(String name,String url) {
    this.name=name;
    this.url=url;
}

@Override
public Object call() throws Exception {
    WebDownload wb = new WebDownload();
    wb.download(name,url);
    System.out.println(name);
    return true;
}

public static void main(String[] args) throws ExecutionException, InterruptedException {
    //创建输入对象
    CDownload t1 = new CDownload("");
    CDownload t2 = new CDownload("");
    CDownload t3 = new CDownload("");

    //执行服务
    ExecutorService ser =  Executors.newFixedThreadPool(3);
    //提交执行
    FutureTask<Object> r1 = ser.submit(t1);
    FutureTask<Object> r2 = ser.submit(t2);
    FutureTask<Object> r3 = ser.submit(t3);
    //获取结果
    Object ret1 = r1.get();
    Object ret2 = r2.get();
    Object ret3 = r3.get();
    System.out.println(ret1 + "----" + ret2 + "----" + ret3 );
    
    
    // 关闭服务器
    ser.shoutdown();



}

}

你在调用submit时报了编译错误,你传入的参数类型应该是跟定义submit时定义的参数类型不一致,
如果没问题,检查一下导入的包,是不是调错了方法