Counts the number of words in a String

CountWords.kt

import java.text.BreakIterator

fun String.countWords(): Int {
    fun isWord(word: String): Boolean {
        if (word.length == 1) {
            return word[0].isLetterOrDigit()
        }
        return "" != word.trim()
    }

    val iterator = BreakIterator.getWordInstance()
    iterator.setText(this)

    var wordCount = 0
    var start = 0
    var end = iterator.first()
    while (end != BreakIterator.DONE) {
        val word = substring(start, end)
        if (isWord(word)) {
            wordCount++
        }
        start = end
        end = iterator.next()
    }
    return wordCount
}