Is there a better way to check a string contains b...

# codereview

[Simon Lin]

Is there a better way to check a string contains both number and alphabet?

val text = "aas211w"
if (text.any { it.isDigit() } && text.any { it.isLetter() }) {
}

[ephemient]

depends on what you want. note that (due to Char's 16-bit nature)

"Ｓ".any { it.isLetter() } == true
"𐐠".any { it.isLetter() } == false

[Tobias Suchalla]

any also only checks if at least one of the chars matches the predicate, I suspect you might want all :

val text = "aas211w"
if (text.all { it.isDigit() || it.isLetter() }) {
    // do something
}

[Matteo Mirk]

val text = """aas211W𐐠Ｓ""" // contains UTF8 letters
text.matches("""[\p{L}\d]+""".toRegex()) // true, UTF8-inclusive

[Matteo Mirk]

if you just need to match ASCII letters the regex becomes """[a-zA-Z\d]+"""

[Klitos Kyriacou]

I was wondering what you meant by "contains UTF8 letters". A String doesn't normally contain UTF8, that's just an encoding scheme for converting bytes into characters code points. I presume you meant your source code contained UTF8 letters, but once parsed and stored in a String they are just Unicode letters.

[Matteo Mirk]

Sorry, my mistake, I confused terms: I meant unicode letters outside of the ASCII range. I used the wrong word, the encoding in place of the code points.

[brandonmcansh]

isn't there an isLetterOrDigit() in the JVM already?

[Matteo Mirk]

there is an extension method in Kotlin SDK since 1.0: fun Char.isLetterOrDigit(): Boolean
an yes, there are the static methods in the Char class
• public static boolean isLetterOrDigit(char ch) since Java 1
• public static boolean isLetterOrDigit(int codePoint) since Java 5
good catch Brandon, I totally forgot those!

[ephemient]

back to the original question… if the desire is to do something like those vexing password rules (must have a digit, must have a letter) then .isLetterOrDigit() doesn't help, but the original can be modified to be Unicode-safe on JVM:

"aas211w".codePoints()
    .map { if (Character.isDigit(it)) 1 else if (Character.isletter(it)) 2 else 0 }
    .reduce(0, Int::or) == 3

[ephemient]

or if Java 8+ isn't available, something like generateSequence(0) { offsetByCodePoints(it, 1) }.takeWhile { it < length }.map { codePointAt(it) } instead of .codePoints()