线程池执行execute()方法和submit()方法的区别是什么呢？

public class callThread implements Callable {
    int key;

    public callThread(int key) {
        this.key = key;
    }

    @Override
    public Integer call() throws Exception {
        return key ;
    }
}

public class ThreadCount {
    static volatile int  a=1;
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        CountDownLatch  countDownLatch=new CountDownLatch(a);
        ExecutorService threadPool = Executors.newCachedThreadPool();
        int o1,o2;
        {
            o1 = (int) threadPool.submit(new callThread(20)).get();
            o2 = (int) threadPool.submit(new callThread(25)).get();
            countDownLatch.countDown();
        }
        countDownLatch.await();
        System.out.println(o1+o2);
    }
}