//创建一个线程池
ExecutorService pool = Executors.newFixedThreadPool(100);
//创建多个有返回值的任务
List<Future> list = new ArrayList<Future>();
for (int i = 0; i < 100; i++) {
    int finalI = i;
    Callable callable = () -> {
        return finalI;
    };
    //执行任务并获取 Futrue对象
    Future f = pool.submit(callable);
    list.add(f);
}
//关闭线程池 停止新任务提交，执行完成之前提交的任务
pool.shutdown();

for (Future future : list) {
    System.out.println("i:" + future.get().toString());
}