blocks|key|58|text|toIntOrNull函数在kotlin.text包中(在kotlin-stdlib中)可能是您要寻找的：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|59|toIntOrNull
有趣的String.toIntOrNull()：Int？(来源)
平台和版本要求:+Kotlin+1.1
将字符串解析为Int数字，如果字符串不是数字的有效表示形式，则返回结果或null。
有趣的String.toIntOrNull(基:+Int)：Int？(来源)
平台和版本要求:+Kotlin+1.1
将字符串解析为Int数字，如果字符串不是数字的有效表示形式，则返回结果或null。|blockquote|BOLD|60|更多信息：https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/to-int-or-null.html|61|entityMap|0|LINK|mutability|MUTABLE|url|https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/to-int-or-null.html^0|0|B|E|B|T|D|0|0|B|0|5|24|0|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]|$9|W|A|X|B|C]|$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|10|8|@$9|11|A|12|B|I]]|D|@]|E|$]]|$1|J|3|K|5|6|7|13|8|@]|D|@$9|14|A|15|1|16]]|E|$]]|$1|L|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|M|$N|$5|O|P|Q|E|$R|S]]]]

The <code>toIntOrNull</code> function in the <code>kotlin.text</code> package (in <code>kotlin-stdlib</code>) is probably what you're looking for:

<blockquote>
 toIntOrNull

<pre><code>fun String.toIntOrNull(): Int? (source)
</code></pre>
 
 Platform and version requirements: Kotlin 1.1
 
 Parses the string as an Int number and returns the result or null if the string is not a valid representation of a number.

<pre><code>fun String.toIntOrNull(radix: Int): Int? (source)
</code></pre>
 
 Platform and version requirements: Kotlin 1.1
 
 Parses the string as an Int number and returns the result or null if the string is not a valid representation of a number.
</blockquote>

More information: <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/to-int-or-null.html" rel="noreferrer">https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/to-int-or-null.html</a>

blocks|key|637823|text|版本1(根据请求使用+toIntOrNull+和)|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|637824|fun+String.intOrString():+Any+{
++++val+v+=+toIntOrNull()
++++return+when(v)+{
++++++++null+->+this
++++++++else+->+v
++++}
}

"4".intOrString()+//+4
"x".intOrString()+//+x|code-block|syntax|javascript|637825|版本2(使用+toIntOrNull+和elvis运算符)|637826|when实际上不是处理这个问题的最佳方法，我使用when只是因为您明确地要求使用它。这样做更合适：|CODE|637827|fun+String.intOrString()+=+toIntOrNull()+?:+this|637828|版本3(使用异常处理)：|637829|fun+String.intOrString()+=+try+{+//+returns+Any
+++toInt()
}+catch(e:+NumberFormatException)+{
+++this
}|637830|entityMap|0|LINK|mutability|MUTABLE|url|https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/to-int-or-null.html|1^0|0|A|N|2|B|B|0|0|0|0|6|J|A|7|B|1|0|0|1D|0|4|O|4|0|0|0|C|0|0^^$0|@$1|2|3|4|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]]|D|@$9|19|A|1A|1|1B]]|E|$]]|$1|F|3|G|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1D|8|@$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]]|D|@$9|1I|A|1J|1|1K]]|E|$]]|$1|M|3|N|5|6|7|1L|8|@$9|1M|A|1N|B|C]|$9|1O|A|1P|B|O]|$9|1Q|A|1R|B|O]]|D|@]|E|$]]|$1|P|3|Q|5|H|7|1S|8|@]|D|@]|E|$I|J]]|$1|R|3|S|5|6|7|1T|8|@$9|1U|A|1V|B|C]]|D|@]|E|$]]|$1|T|3|U|5|H|7|1W|8|@]|D|@]|E|$I|J]]|$1|V|3|-4|5|6|7|1X|8|@]|D|@]|E|$]]]|W|$X|$5|Y|Z|10|E|$11|12]]|13|$5|Y|Z|10|E|$11|12]]]]

Version 1 (using <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/to-int-or-null.html" rel="noreferrer"><code>toIntOrNull</code></a> and <code>when</code> when as requested)

<pre><code>fun String.intOrString(): Any {
 val v = toIntOrNull()
 return when(v) {
 null -&gt; this
 else -&gt; v
 }
}

"4".intOrString() // 4
"x".intOrString() // x
</code></pre>

Version 2 (using <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/to-int-or-null.html" rel="noreferrer"><code>toIntOrNull</code></a> and the elvis operator <code>?:</code>)

<code>when</code> is actually not the optimal way to handle this, I only used <code>when</code> because you explicitely asked for it. This would be more appropriate:

<pre><code>fun String.intOrString() = toIntOrNull() ?: this
</code></pre>

Version 3 (using exception handling):

<pre><code>fun String.intOrString() = try { // returns Any
 toInt()
} catch(e: NumberFormatException) {
 this
}
</code></pre>

blocks|key|224|text|使用let作为一个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|225|fun+isInteger(str:+String?)+=+str?.toIntOrNull()?.let+{+true+}+?:+false|code-block|syntax|javascript|226|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Using let for one

<pre><code>fun isInteger(str: String?) = str?.toIntOrNull()?.let { true } ?: false
</code></pre>

blocks|key|1272138|text|如果要检查字符串是否为数字(Int)，并执行一些简单的解决方案，可以如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1272139|if+(myString.toIntOrNull()+!=+null)+{
+++//Write+your+code+you+want+to+execute+if+myString+is+(Int)
}+else+{
+++//Write+your+code+you+want+to+execute+if+myString+is+(not+Int)
}|code-block|syntax|javascript|1272140|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you want to check if it is numeric (Int) the string and do something a simple solution could be:
<pre><code>if (myString.toIntOrNull() != null) {
 //Write your code you want to execute if myString is (Int)
} else {
 //Write your code you want to execute if myString is (not Int)
}
</code></pre>

blocks|key|267|text|我搜索了同样的答案，因此我从上面的答案中找到了自己的答案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|268|//function+to+check+strin+is+int+or+bull
fun+String.intOrString():+Boolean{
++++val+v+=+toIntOrNull()
++++return+when(v)+{
+++++++null+->+false
++++++++else+->+true
++++}
}|code-block|syntax|javascript|269|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I searched for the same and I found this answer so I have made my own version from the above answer:
<pre><code>//function to check strin is int or bull
fun String.intOrString(): Boolean{
 val v = toIntOrNull()
 return when(v) {
 null -&gt; false
 else -&gt; true
 }
}
</code></pre>

blocks|key|638449|text|简单直观|type|unstyled|depth|inlineStyleRanges|entityRanges|data|638450|fun+isNumeric(str:+String)+=+str.all+{+it+in+'0'..'9'+}|code-block|syntax|javascript|638451|正如@coolMind所指出的，如果您想要过滤%2B/-|638452|fun+isNumeric(str:+String):+Boolean+=+str
++++++++.removePrefix("-")
++++++++.removePrefix("%2B")
++++++++.all+{+it+in+'0'..'9'+}|638453|表演也会很相似|638454|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Simple and intuitive
<pre class="lang-kotlin prettyprint-override"><code>fun isNumeric(str: String) = str.all { it in '0'..'9' }
</code></pre>
As @coolMind point out, if you want to filter +/-
<pre class="lang-kotlin prettyprint-override"><code>fun isNumeric(str: String): Boolean = str
 .removePrefix(&quot;-&quot;)
 .removePrefix(&quot;+&quot;)
 .all { it in '0'..'9' }
</code></pre>
The performance would be similar

blocks|key|380|text|共享Regex匹配解决方案，从我的答案这里中转发|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|381|如果可以用'-‘和’‘格式化的负数和正数，则是最合适的解决方案。|382|如果格式化字符串号与regex模式匹配，则下面的方法返回true。|383|fun+isPosOrNegNumber(s:+String?)+:+Boolean+{
++++val+regex+=+"""%5E(-)?[0-9]{0,}((\.){1}[0-9]{1,}){0,1}$""".toRegex()
++++return+if+(s.isNullOrEmpty())+false+
+++++++++++else+regex.matches(s)++++++++++++
}|code-block|syntax|javascript|384|​|385|📷|atomic|386|387|上面的示例正则表达式仅适用于美国数字格式，但如果您想使用EU数字格式，则只需替换“。”在regex模式字符串中使用'，‘|388|注：。如果数字包含逗号，那么只需在发送到此方法时替换它，或者更好地形成带有逗号的regex模式。|389|entityMap|0|LINK|mutability|MUTABLE|url|https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/-regex/matches.html|1|https://stackoverflow.com/a/69282734/7873768|2|IMAGE|IMMUTABLE|imageUrl|https://developer.qcloudimg.com/http-save/yehe-900000/be7b0f7de8f01e4262f71995b1df0b51.png|imageAlt^0|2|7|0|J|2|1|0|0|0|0|0|0|1|2|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1C|8|@]|9|@$A|1D|B|1E|1|1F]|$A|1G|B|1H|1|1I]]|C|$]]|$1|D|3|E|5|6|7|1J|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|1K|8|@]|9|@]|C|$]]|$1|H|3|I|5|J|7|1L|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|1M|8|@]|9|@]|C|$]]|$1|O|3|P|5|Q|7|1N|8|@]|9|@$A|1O|B|1P|1|1Q]]|C|$]]|$1|R|3|N|5|6|7|1R|8|@]|9|@]|C|$]]|$1|S|3|T|5|6|7|1S|8|@]|9|@]|C|$]]|$1|U|3|V|5|6|7|1T|8|@]|9|@]|C|$]]|$1|W|3|-4|5|6|7|1U|8|@]|9|@]|C|$]]]|X|$Y|$5|Z|10|11|C|$12|13]]|14|$5|Z|10|11|C|$12|15]]|16|$5|17|10|18|C|$19|1A|1B|-4]]]]

Sharing <a href="https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/-regex/matches.html" rel="nofollow noreferrer">Regex matches</a> solution, repost from my answer <a href="https://stackoverflow.com/a/69282734/7873768">here</a>
Best suited solution if negative and positive number which can be formatted with '-' and '.'
below method returns true if formatted string number matches the regex pattern
<pre><code>fun isPosOrNegNumber(s: String?) : Boolean {
 val regex = &quot;&quot;&quot;^(-)?[0-9]{0,}((\.){1}[0-9]{1,}){0,1}$&quot;&quot;&quot;.toRegex()
 return if (s.isNullOrEmpty()) false 
 else regex.matches(s) 
}
</code></pre>
<a href="https://i.stack.imgur.com/PiHS9.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PiHS9.png" alt="enter image description here" /></a>
Above sample regex is only for US number formats but if you want to use EU number formats then just replace '.' with ',' in regex pattern string
Note:. if the numbers contain commas then just replace it while sending to this method or better form a regex pattern with commas in it.

I'd like to use a <code>when()</code> expression in Kotlin to return different values from a function. The input is a <code>String</code>, but it might be parsable to an <code>Int</code>, so I'd like to return the parsed <code>Int</code> if possible, or a <code>String</code> if it is not. Since the input is a <code>String</code>, I cannot use the is type check expression.
Is there any idiomatic way to achieve that?
My problem is what the <code>when()</code> expression should look like, not about the return type.

How to use Kotlin to find whether a string is numeric?

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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我想使用Kotlin中的when()表达式从函数返回不同的值。输入是一个String，但是它可能被解析为一个Int，所以如果可能的话，我想返回解析的Int，如果不是的话，返回一个String。因为输入是一个String，所以我不能使用is类型check表达式。有什么惯用的方法来达到这个目的吗？我的问题是when()表达...

问如何使用Kotlin查找字符串是否为数字？
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问如何使用Kotlin查找字符串是否为数字？EN