kotlin split utf string into single length sub strings using codepoint - unicode

Question

I'm just starting kotlin so I'm sure there is an easy way to do this but I don't see it. I want to split a into single-length sub strings using codepoints. In Java 8, this works:
public class UtfSplit {
static String [] utf8Split (String str) {
int [] codepoints = str.codePoints().toArray();
String [] rv = new String[codepoints.length];
for (int i = 0; i < codepoints.length; i++)
rv[i] = new String(codepoints, i, 1);
return rv;
}
public static void main(String [] args) {
String test = "こんにちは皆さん";
System.out.println("Test string:" + test);
StringBuilder sb = new StringBuilder("Result:");
for(String s : utf8Split(test))
sb.append(s).append(", ");
System.out.println(sb.toString());
}
}
Output is:
Test string:こんにちは皆さん
Result:こ, ん, に, ち, は, 皆, さ, ん,
How would I do this in kotlin?? I can get to codepoints although it's clumsy and I'm sure I'm doing it wrong. But I can't get from the codepoints back to a strings. The whole string/character interface seems different to me and I'm just not getting it.
Thanks
Steve S.

Answer 1

You are using the same runtime as Java so the code is basically doing the same thing. However, the Kotlin version is shorter, and also has no need for a class, although you could group utility methods into an object. Here is the version using top-level functions:
fun splitByCodePoint(str: String): Array<String> {
val codepoints = str.codePoints().toArray()
return Array(codepoints.size) { index ->
String(codepoints, index, 1)
}
}
fun main(args: Array<String>) {
val input = "こんにちは皆さん"
val result = splitByCodePoint(input)
println("Test string: ${input}")
println("Result: ${result.joinToString(", ")}")
}
Output:
Test string: こんにちは皆さん
Result: こ, ん, に, ち, は, 皆, さ, ん
Note: I renamed the function because the encoding doesn't really matter since you are just splitting by Codepoints.
Some might write this without the local variable:
fun splitByCodePoint(str: String): Array<String> {
return str.codePoints().toArray().let { codepoints ->
Array(codepoints.size) { index -> String(codepoints, index, 1) }
}
}
See also:
Kotlin stdlib Array initializer by index w/lambda
Kotlin stdlib let function