blocks|key|315374|text|当您知道如何立即做出反应和/或期望元素不存在时，请使用轮询。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|315375|否则，请使用remove。|315376|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

When you know how to react right now and/or expect elements to be absent then use poll.

Otherwise use remove.

blocks|key|320204|text|有时，您希望为空队列返回空值，有时，您希望它将空队列视为异常情况。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|320205|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Sometimes you want a null value returned for an empty queue and sometimes you want it to treat an empty queue as a exception case.

blocks|key|3277027|text|在关于队列结构的经典讨论中，这两种方法的用法不同。我主要使用poll()来检索项，如果需要在正常循环之外修改队列，则主要使用remove()。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3277028|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The two methods are used differently in classic discussions about a Queue structure. I use poll() mostly to retrieve items, and remove() mostly if I need to modify the Queue outside of the normal loop.

blocks|key|3277067|text|在某些情况下，预计队列将是空的，在这些情况下，使用不抛出异常的方法是合适的。在其他情况下，队列是空的是一种异常情况，异常是合适的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3277068|抛出异常会导致性能损失，如果您希望队列不时为空，那么您不希望必须将队列-空-逻辑作为捕获异常来处理-它既昂贵又难以读取。|3277069|在相反的情况下，你不希望队列为空，这是编程错误的标志，或者是其他一些异常情况，你不想编写丑陋的错误条件检查代码(例如，检查null)，因为在这种情况下，这将比捕获异常(这可以在另一个作用域中完成)的可读性更差。|3277070|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

In some situations it's expected that a queue will be empty, and in those cases having a method that doesn't throw an exception is appropriate. In other situations it's an exceptional circumstance that the queue is empty, and an exception is appropriate.

Throwing exceptions incurs a performance penalty, and if it's the case that you expect the queue to be empty from time to time you don't want to have to handle the queue-empty-logic as catching an exception -- it's both costly and difficult to read.

In the opposite case where you don't expect the queue to ever be empty it is a sign of a programming error, or some other exceptional circumstance that it is, and you don't want to write ugly error condition checking code (e.g. checking for null), because in this case that would be less readable than catching an exception (which you can do in another scope).

blocks|key|3277077|text|抽象类AbstractQueue<E>实现了Queue<E>并定义了remove方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3277078|你可以看一下源代码：|3277079|public+E+remove()+{
++++E+x+=+poll();
++++if+(x+!=+null)
++++++++return+x;
++++else
++++++++throw+new+NoSuchElementException();
}|code-block|syntax|javascript|3277080|因此，正如您所看到的，remove()方法使用+poll()方法。|BOLD|3277081|你可以使用你喜欢的那一个。|3277082|entityMap^0|3|G|M|8|0|0|0|B|8|O|6|L|2|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Z|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|O]]|D|@]|E|$]]|$1|P|3|Q|5|6|7|17|8|@]|D|@]|E|$]]|$1|R|3|-4|5|6|7|18|8|@]|D|@]|E|$]]]|S|$]]

The abstract class <code>AbstractQueue&lt;E&gt;</code> implements <code>Queue&lt;E&gt;</code> and define the remove method.

You can take a look at source code:

<pre><code>public E remove() {
 E x = poll();
 if (x != null)
 return x;
 else
 throw new NoSuchElementException();
}
</code></pre>

So, as you can see, the <code>remove()</code> method use <code>poll()</code> method.

You can use which one you prefer.

blocks|key|318450|text|看着答案，我不清楚是谁做的，因此：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|318451|remove()和()方法只在队列为空时的行为不同:+remove()方法抛出异常，而()方法返回null|offset|length|style|BOLD|318452|entityMap^0|0|9|Y|0^^$0|@$1|2|3|4|5|6|7|J|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|K|8|@$D|L|E|M|F|G]]|9|@]|A|$]]|$1|H|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|I|$]]

Looking at the answers, it wasn't clear to me which did what,hence:

Straight from the API : 
The remove() and poll() methods differ only in their behavior when the queue is empty: the remove() method throws an exception, while the poll() method returns null

blocks|key|3064188|text|Remove()方法与poll的唯一不同之处在于，如果此队列为空，它将抛出异常。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3064189|​|3064190|📷|atomic|3064191|3064192|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/6e850481866c84266417ced9572a8cbf.png|imageAlt^0|0|8|0|0|0|1|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|X|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|Y|8|@]|D|@$9|Z|A|10|1|11]]|E|$]]|$1|K|3|G|5|6|7|12|8|@]|D|@]|E|$]]|$1|L|3|-4|5|6|7|13|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|S|T|-4]]]]

<code>Remove()</code> method differs from poll only in that it throws an exception if this queue is empty.

<img src="https://i.stack.imgur.com/9OwTf.png" alt="enter image description here">

The <code>Queue</code> implementation in Java has two methods to remove element, One is <code>remove()</code> which throws exception and other one is <code>poll()</code> which returns <code>null</code> for an empty queue. I have two doubts:

<ol>
<li>Why <code>Queue</code> has different implementation to remove element?</li>
<li>Which implementation to use When?</li>
</ol>

Why Java provides two methods to remove element from Queue?

Java

Java中的Queue实现有两种方法来移除元素，一种是抛出异常的remove()方法，另一种是为空队列返回null的poll()方法。我有两个疑问：为什么Queue有不同的实现来删除元素？在什么情况下使用哪个实现？

问为什么Java提供了两种从队列中删除元素的方法？
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