使用多线程 执行有返回值的方法

public class ThreadTest {

    private static BlockingQueue<Runnable> queue = new ArrayBlockingQueue<Runnable>(50000);
    public static ThreadPoolExecutor executor;

    static {
        executor = new ThreadPoolExecutor(15, 100, 60L,
            TimeUnit.SECONDS, queue, new ThreadPoolExecutor.AbortPolicy());
    }

    public static void main(String[] args) {

        List<Future> futureList = new ArrayList<>();
        for (int i = 0; i < 10; i++) {
            final int  a = i;
            Future futureString = executor.submit((Callable<Object>)() -> handle(a));
            futureList.add(futureString);
        }

        int sum = 0;
        for (Future future : futureList) {
            Integer returnint = (Integer)getFutureObject(future);
            System.out.println(returnint +"  " +  new Date());
            sum = sum + returnint;
        }
        System.out.println(sum);
    }

    public static int handle(int num) {
        int sleepNUM = 10 - num;

        System.out.println("num strart " + num +"  "+ new Date());
        try {
            Thread.sleep(sleepNUM * 1000);
        }catch (Exception e){}
        System.out.println("num end " + num +"  " +  new Date() );

        return num;

    }

    private static Object getFutureObject(Future future){
        try {
            return future.get(600, TimeUnit.SECONDS);
        }catch (Exception ex){
        }
        return null;
    }
}

---------------------------

num strart 3 Thu May 28 01:55:02 CST 2020
num strart 6 Thu May 28 01:55:02 CST 2020
num strart 1 Thu May 28 01:55:02 CST 2020
num strart 8 Thu May 28 01:55:02 CST 2020
num strart 4 Thu May 28 01:55:02 CST 2020
num strart 0 Thu May 28 01:55:02 CST 2020
num strart 2 Thu May 28 01:55:02 CST 2020
num strart 5 Thu May 28 01:55:02 CST 2020
num strart 7 Thu May 28 01:55:02 CST 2020
num strart 9 Thu May 28 01:55:02 CST 2020
num end 9 Thu May 28 01:55:03 CST 2020
num end 8 Thu May 28 01:55:04 CST 2020
num end 7 Thu May 28 01:55:05 CST 2020
num end 6 Thu May 28 01:55:06 CST 2020
num end 5 Thu May 28 01:55:07 CST 2020
num end 4 Thu May 28 01:55:08 CST 2020
num end 3 Thu May 28 01:55:09 CST 2020
num end 2 Thu May 28 01:55:10 CST 2020
num end 1 Thu May 28 01:55:11 CST 2020
num end 0 Thu May 28 01:55:12 CST 2020
0 Thu May 28 01:55:12 CST 2020
1 Thu May 28 01:55:12 CST 2020
2 Thu May 28 01:55:12 CST 2020
3 Thu May 28 01:55:12 CST 2020
4 Thu May 28 01:55:12 CST 2020
5 Thu May 28 01:55:12 CST 2020
6 Thu May 28 01:55:12 CST 2020
7 Thu May 28 01:55:12 CST 2020
8 Thu May 28 01:55:12 CST 2020
9 Thu May 28 01:55:12 CST 2020
45