Queue队列中，poll() 和 remove() 都是从队列中取出一个元素，在队列元素为空的情况下，remove() 方法会抛出异常，poll() 方法只会返回 null 。

我们再来看一下源码的解释：

/**

* Retrieves and removes the head of this queue. This method differs

* from {@link #poll poll} only in that it throws an exception if this

* queue is empty.

*

* @return the head of this queue

* @throws NoSuchElementException if this queue is empty

*/

E remove();

/**

* Retrieves and removes the head of this queue,

* or returns {@code null} if this queue is empty.

*

* @return the head of this queue, or {@code null} if this queue is empty

*/

E poll();