你可以看看here，有很多例子。
例如，您可以通过

fun isLetters(string: String): Boolean {
    return string.all { it.isLetter() }
}

检查String是否完全按字母顺序排列的一个很好的答案是由@HakobHakobyan给出的：String.all { it.isLetter() }。
我将借用他的解决方案来针对你问题的第二个方面，即

• 输入可以是任何东西，字符串，int或double等 *

下面是另一个检查Any输入类型的方法：

fun isAplhabetical(input: Any): Boolean {
    when (input) {
        // if the input is a String, check all the Chars of it
        is String -> return input.all { it.isLetter() }
        // if input is a Char, just check that single Char
        is Char -> return input.isLetter()
        // otherwise, input doesn't contain any Char
        else -> return false
    }
}

它可以用在main()这样的例子中：

fun main() {
    val a = "Some non-numerical input"
    val b = "45"
    val c = "Some numbers, like 1, 2, 3, 4 and so on"
    val d: Int = 42
    val e: Double = 42.42
    val f: Float = 43.4333f
    val g = "This appears as entirely alphabetical" // but contains whitespaces
    val h = "ThisIsEntirelyAlphabetical"
    
    println("[$a] is" + (if (isAplhabetical(a)) "" else " not") + " (entirely) alphabetical")
    println("[$b] is" + (if (isAplhabetical(b)) "" else " not") + " (entirely) alphabetical")
    println("[$c] is" + (if (isAplhabetical(c)) "" else " not") + " (entirely) alphabetical")
    println("[$d] is" + (if (isAplhabetical(d)) "" else " not") + " (entirely) alphabetical")
    println("[$e] is" + (if (isAplhabetical(e)) "" else " not") + " (entirely) alphabetical")
    println("[$f] is" + (if (isAplhabetical(f)) "" else " not") + " (entirely) alphabetical")
    println("[$g] is" + (if (isAplhabetical(g)) "" else " not") + " (entirely) alphabetical")
    println("[$h] is" + (if (isAplhabetical(h)) "" else " not") + " (entirely) alphabetical")
}

输出是

[Some non-numerical input] is not (entirely) alphabetical
[45] is not (entirely) alphabetical
[Some numbers, like 1, 2, 3, 4 and so on] is not (entirely) alphabetical
[42] is not (entirely) alphabetical
[42.42] is not (entirely) alphabetical
[43.4333] is not (entirely) alphabetical
[This appears as entirely alphabetical] is not (entirely) alphabetical
[ThisIsEntirelyAlphabetical] is (entirely) alphabetical

只有最后一个String完全是字母顺序。

你可以使用正则表达式和字母表范围：

fun alphabetCheck(input: String): Boolean {
    val regex = Regex("[a-zA-Z]+?")
    return regex.matches(input)
}

首先使用toString()将输入转换为字符串：

val str = input.toString()
val matchesAlphabet = alphabetCheck(str)

你可以检查一个字符的值，如示例所示：

fun main(args: Array) {

    val c = 'a'
    val ascii = c.toInt()

    println("The ASCII value of $c is: $ascii")
}

如果您查看ascii table，您可以看到字母字符是大写字母的值65和90之间的字符。对于小写字母，间隔为97 - 122。

如果你想构建一个任意的查找（比如适合base64编码的字符），你也可以这样做：

val acceptable = ('a'..'z').plus('A'..'Z').plus("+-/~".asIterable())

所以这是使用范围作为一种快速的方式来定义一个...字符范围，并使用字符串轻松指定一些单个字符（并将其转换为Iterable<Char>，以便plus可以将它们添加到列表中。

val Char.isAcceptable get() = this in acceptable

"ab+5%".filter(Char::isAcceptable).let { print("VIPs: $it")}
>>>> VIPs: ab+

可以按如下方式完成：

fun checkDigitOrLetter(c: Char) = when (c) {
   in '0'..'9' -> "Digit!"
   in 'a'..'z', in 'A'..'Z' -> "Letter!" 
   else -> "None"
}