Java用FutureTask实现又返回值的线程

要实现有返回值的多线程，具体代码如下：

package thread;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class App {

    public static class MySum implements Callable<Integer> {

        @Override
        public Integer call() throws Exception {
            System.out.println("准备计算");
            Thread.sleep(2000);
            int sum = 0;
            for (int i = 0; i < 5000; i++) {
                sum += i;
            }
            System.out.println("计算结果:" + sum);
            return sum;
        }

    }

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        MySum mysum=new MySum();
        FutureTask<Integer> futureTask=new FutureTask<>(mysum);
        new Thread(futureTask).start();
        System.out.println("主线程的最终结果是:"+futureTask.get());
    }

}

1.FutureTask实现了接口Runnable，所以可以传入到线程中执行

2.futureTask.get()是一个阻塞方法

3.Callable<Integer>中的Integer表示返回的数据类型