blocks|key|173554|text|幂等意味着您可以多次应用该操作，但一个调用的结果状态将无法与多个调用的结果状态区分开来。简而言之，多次调用该方法是安全的。实际上，第二次和第三次(以此类推)调用将不会对程序的状态产生明显影响。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|173555|所以如果你关闭这个对象一次，它就关闭了，你没有足够的信息来知道它是否是幂等的。然而，如果你关闭它两次，第一次关闭，但第二次抛出异常，它显然不是幂等的。另一方面，如果您关闭它一次，然后关闭它两次，而第二个关闭导致项以相同的方式保持关闭(可能它是一个noop)，那么它是幂等的。|173556|制作幂等Closeable的一种技术可能是：|offset|length|style|CODE|173557|public+class+Example+implements+Closeable+{

++private+boolean+closed;

++public+Example()+{
++++closed+=+false;
++}

++public+void+close()+{
++++if+(!isClosed())+{
++++++closed+=+true;
++++}
++}

++public+boolean+isClosed()+{
++++return+closed;
++}
}|code-block|syntax|javascript|173558|现在很明显，如果close()被调用一次或多次，则通过isClosed()返回的所有状态都将永远返回true。因此，方法close()将被认为是幂等的。|173559|entityMap^0|0|0|4|9|0|0|8|7|R|A|1O|7|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|U|8|@$F|V|G|W|H|I]]|9|@]|A|$]]|$1|J|3|K|5|L|7|X|8|@]|9|@]|A|$M|N]]|$1|O|3|P|5|6|7|Y|8|@$F|Z|G|10|H|I]|$F|11|G|12|H|I]|$F|13|G|14|H|I]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|R|$]]

Idempotent means that you can apply the operation a number of times, but the resulting state of one call will be indistinguishable from the resulting state of multiple calls. In short, it is safe to call the method multiple times. Effectively the second and third (and so on) calls will have no visible effect on the state of the program.

So if you close this object once, and it closes, you don't have enough information to know if it is idempotent. However, if you close it twice, and the first time it closes, but the second time it throws an exception, it is clearly not idempotent. On the other hand, if you close it once, and close it twice, and the second closure results in the item remaining closed in the same manner (perhaps it is a noop), then it is idempotent.

One technique of making an idempotent <code>Closeable</code> could be:

<pre><code>public class Example implements Closeable {

 private boolean closed;

 public Example() {
 closed = false;
 }

 public void close() {
 if (!isClosed()) {
 closed = true;
 }
 }

 public boolean isClosed() {
 return closed;
 }
}
</code></pre>

Where it is now obvious that if <code>close()</code> is called once or multiple times, all returns of the state through <code>isClosed()</code> will forever return true. Therefore, the method <code>close()</code> would be considered idempotent.

blocks|key|173604|text|没有代码的概念的解释|type|unstyled|depth|inlineStyleRanges|entityRanges|data|173605|​|173606|📷|atomic|offset|length|173607|173608|对于adopt+Einstein's+aphorism来说，如果你做同样的事情，得到不同的结果，那么这个方法就不是幂等的。|173609|幂等性的示例|173610|"Please+sir,+can+I+have+a+pay+rise?"

"No"|code-block|syntax|javascript|173611|Same+result+every+time。要求加薪是一个幂等操作。|173612|HTTP请求的示例：|173613|173614|发出get请求:如果正确实现，则无论您发出此请求多少次，都将得到相同的响应。例如，|unordered-list-item|style|CODE|173615|一个不是幂等的操作将发出一个创建资源的post请求-每次执行此操作时，您都会更改要将其发布到的应用程序的状态:每次都会创建一个新资源！|173616|173617|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/fb095f315f6e62b485a1087aac215b46.jpeg|imageAlt|1|LINK|MUTABLE|url|https://www.scientificamerican.com/article/einstein-s-parable-of-quantum-insanity/|2|https://www.youtube.com/watch?v=7tOkpntQtBM^0|0|0|0|1|0|0|0|2|P|1|0|0|0|0|M|2|0|0|0|2|3|0|J|4|0|0^^$0|@$1|2|3|4|5|6|7|1L|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|1M|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|1N|8|@]|9|@$G|1O|H|1P|1|1Q]]|A|$]]|$1|I|3|C|5|6|7|1R|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|1S|8|@]|9|@$G|1T|H|1U|1|1V]]|A|$]]|$1|L|3|M|5|6|7|1W|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1X|8|@]|9|@]|A|$Q|R]]|$1|S|3|T|5|6|7|1Y|8|@]|9|@$G|1Z|H|20|1|21]]|A|$]]|$1|U|3|V|5|6|7|22|8|@]|9|@]|A|$]]|$1|W|3|-4|5|6|7|23|8|@]|9|@]|A|$]]|$1|X|3|Y|5|Z|7|24|8|@$G|25|H|26|10|11]]|9|@]|A|$]]|$1|12|3|13|5|Z|7|27|8|@$G|28|H|29|10|11]]|9|@]|A|$]]|$1|14|3|-4|5|6|7|2A|8|@]|9|@]|A|$]]|$1|15|3|-4|5|6|7|2B|8|@]|9|@]|A|$]]]|16|$17|$5|18|19|1A|A|$1B|1C|1D|-4]]|1E|$5|1F|19|1G|A|$1H|1I]]|1J|$5|1F|19|1G|A|$1H|1K]]]]

<h1>Explanation of Concept Without Code</h1>
<a href="https://i.stack.imgur.com/uPm53.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uPm53.jpg" alt="Einsteins definition of indempotency" /></a>
To <a href="https://www.scientificamerican.com/article/einstein-s-parable-of-quantum-insanity/" rel="nofollow noreferrer">adopt Einstein's aphorism</a>, if you do the same thing, and get different results, then the method is not idempotent.
<h3>Example of idempotency</h3>
<pre><code>&quot;Please sir, can I have a pay rise?&quot;

&quot;No&quot;
</code></pre>
<a href="https://www.youtube.com/watch?v=7tOkpntQtBM" rel="nofollow noreferrer">Same result every time</a>. Asking for a pay rise is an idempotent operation.
<h3>Examples with HTTP Requests:</h3>
<ul>
<li>Making a <code>get</code> request: If properly implemented then no matter how many times you make this request, you will get the same response.</li>
<li>An operation that is not Idempotent, for example, would be making a <code>post</code> request to create a resource - every time you do this you will be changing state of the application you are posting this to: a new resource will be created every single time!</li>
</ul>

blocks|key|172924|text|术语表幂等|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|172925|如果方法的编写方式使得对同一方法的重复调用不会导致重复更新，则该方法称为“幂等”。|172926|在数学中，幂等元，或简称为幂等元，是指当乘以自身时，作为结果的任何东西。例如，只有0和1这两个实数是幂等的。|172927|在用户界面设计中，如果一个按钮被多次按下，其效果与按一次按钮的效果相同，那么它可以被称为“幂等按钮”。例如，如果“暂停”按钮切换了暂停状态，那么它就不是幂等按钮。另一方面，如果多次按下它会使系统暂停，并且继续按“播放”，那么“暂停”就是幂等的。这在诸如红外遥控器和触摸屏的界面中是有用的，在这些界面中，用户可能不确定已经成功地按下了按钮，并且可能再次按下该按钮。电梯呼叫按钮也是幂等的，尽管许多人认为它们不是。|172928|资源：-http://www.allapplabs.com/glossary/idempotent.htm|172929|entityMap|0|LINK|mutability|MUTABLE|url|http://www.allapplabs.com/glossary/idempotent.htm^0|0|5|0|11|2|0|0|0|4|1D|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@$9|W|A|X|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Y|8|@$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|11|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|12|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|N|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|O|$P|$5|Q|R|S|E|$T|U]]]]

JAVA GLOSSARY
Idempotent

If methods are written in such a way that repeated calls to the same method do not cause duplicate updates, the method is said to be "idempotent."

In mathematics an idempotent element, or an idempotent for short, is anything that, when multiplied by itself, gives itself as result. For example, the only two real numbers which are idempotent are 0 and 1.

In user interface design, a button can be called "idempotent" if pressing it more than once will have the same effect as pressing it once. For example, a "Pause" button is not idempotent if it toggles the paused state. On the other hand, if pressing it multiple times keeps the system paused and pressing "Play" resumes, then "Pause" is idempotent. This is useful in interfaces such as infrared remote controls and touch screens where the user may not be sure of having pressed the button successfully and may press it again. Elevator call buttons are also idempotent, though many people think they are not. 

Resource:-<a href="http://www.allapplabs.com/glossary/idempotent.htm" rel="noreferrer">http://www.allapplabs.com/glossary/idempotent.htm</a>

blocks|key|173646|text|集成方法|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|173647|如果每次调用的结果都相同，则方法是HTTP方法的幂等方法。当您调用任何请求n次时，结果将是相同的。|173648|举个例子，在任何数字中添加零都会得到相同的结果。|173649|HTTP方法分为两种类型。|173650|173651|安全可重复(Idempotent)|ordered-list-item|173652|Can't可安全重复(非Idempotent)|173653|173654|安全可重复(幂等)：任何时候调用方法，它都会产生相同的结果。它称为幂等方法。|173655|GET，PUT，DELETE+HTTP方法称为幂等方法。因为|173656|GET方法：检索资源。PUT方法：它将更新一个资源。删除方法：用于删除单独的资源，不影响其他资源。|173657|不能是可重复的安全(非幂等)|173658|但是当POST方法调用时。POST方法每次都会创建新的资源。因此称为非幂等元|173659|entityMap^0|0|4|0|O|P|0|0|O|0|0|D|0|0|0|H|0|0|N|0|0|0|12|0|0|U|0|0|1D|0|0|E|0|0|12|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|17|8|@$9|18|A|19|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|1A|8|@$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|J|3|K|5|6|7|1D|8|@$9|1E|A|1F|B|C]]|D|@]|E|$]]|$1|L|3|-4|5|6|7|1G|8|@]|D|@]|E|$]]|$1|M|3|N|5|O|7|1H|8|@$9|1I|A|1J|B|C]]|D|@]|E|$]]|$1|P|3|Q|5|O|7|1K|8|@$9|1L|A|1M|B|C]]|D|@]|E|$]]|$1|R|3|-4|5|6|7|1N|8|@]|D|@]|E|$]]|$1|S|3|T|5|6|7|1O|8|@$9|1P|A|1Q|B|C]]|D|@]|E|$]]|$1|U|3|V|5|6|7|1R|8|@$9|1S|A|1T|B|C]]|D|@]|E|$]]|$1|W|3|X|5|6|7|1U|8|@$9|1V|A|1W|B|C]]|D|@]|E|$]]|$1|Y|3|Z|5|6|7|1X|8|@$9|1Y|A|1Z|B|C]]|D|@]|E|$]]|$1|10|3|11|5|6|7|20|8|@$9|21|A|22|B|C]]|D|@]|E|$]]|$1|12|3|-4|5|6|7|23|8|@]|D|@]|E|$]]]|13|$]]

IDEMPOTENT Methods
HTTP method is imdempotent method if the result become same for every call. When you call any request n times then result would be same.
Take an example that adding ZERO in any number would be the same result.
HTTP methods divided into two types.
<ol>
<li>Safely repeatable (Idempotent)</li>
<li>Can't be repeatable safely (Non- Idempotent)</li>
</ol>
Safely repeatable (Idempotent): Call method any times, it gives same result. it called Idempotent methods.
GET, PUT, DELETE HTTP method called as Idempotent method. Because
GET method: retrieving the resource.
PUT method: It will update one resource.
DELETE method: It will used to delete the indiviual resource not impact other resource.
Can't be repeatable safely (Non- Idempotent)
But when POST method calls.
POST method will create new resource everytime. Therefore it called as Non- Idempotent

Java docs of close() method of java.lang.AutoCloseable says

<blockquote>
 Note that unlike the <a href="https://docs.oracle.com/javase/7/docs/api/java/io/Closeable.html#close()" rel="noreferrer"><code>close()</code></a> method of <a href="https://docs.oracle.com/javase/7/docs/api/java/io/Closeable.html" rel="noreferrer">Closeable</a>, this <code>close()</code> method is
 not required to be idempotent. In other words, calling this close
 method more than once may have some visible side effect, unlike
 <code>Closeable#close()</code> which is required to have no effect if called more
 than once. However, implementers of this interface are strongly
 encouraged to make their close methods idempotent.
</blockquote>

 
What do they mean by idempotent method and what are the side effects of calling this <code>close()</code> method twice?

And since interface <code>Closeable</code> extends <code>AutoCloseable</code> why are the side effects not to be seen in the close of <code>Closeable</code> interface?

What does idempotent method mean and what are the side effects in case of calling close method of java.lang.AutoCloseable?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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java.lang.AutoCloseable的close()方法的Java文档说请注意，与的方法不同，此close()方法不需要是幂等的。换句话说，多次调用此close方法可能会产生一些可见的副作用，这与Closeable#close()不同，后者在多次调用时不会产生任何影响。然而，强烈鼓励此接口的实现者使他们的cl...

问什么是幂等方法，调用java.lang.AutoCloseable的close方法会有什么副作用？
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