实现callable接口加泛型，即返回的值类型，默认为Object

重写的call方法可以有返回值，可以抛出异常

public class ThreadDownload implements Callable<Boolean> {

public Boolean call() throws Exception
{

return true;

}
public static void main(String[]args) throws InterruptedException, ExecutionException
{
ThreadDownload a=new ThreadDownload();
ThreadDownload b=new ThreadDownload();
ThreadDownload c=new ThreadDownload();
//创建执行服务
ExecutorService ser =Executors.newFixedThreadPool(3);
//提交执行
Future<Boolean>result1=ser.submit(a);
Future<Boolean>result2=ser.submit(b);
Future<Boolean>result3=ser.submit(c);
//获取结果
boolean r1=result1.get();
boolean r2=result2.get();
boolean r3=result3.get();
//关闭服务:
ser.shutdownNow();
}
}