Kotlin: Count No of occurrences of string in string

fun main() {
    val s = "5 kg rice 2 kg wheat 3 kg Soya"
    val c = "\\bkg\\b".toRegex().findAll(s).count()
    println(c)
}

This works:

println("5 kg rice 2 kg wheat 3 kg Soya".windowed(2, 1).count { it == "kg" })

But if you only want the occurrences of " kg ", you can use:

println("5 kg rice 2 kg wheat 3 kg Soyakg".windowed(4, 1).count { it == " kg " })

I believe it could work also:

println("5 kg rice 2 kg wheat 3 kg Soya".splitToSequence(" kg ").count() - 1)

As I said before the way you split the string or check the windowed string will depend on what kind of occurrence you consider valid.

The easiest way is:

val count = s.split("kg").size - 1

After you split your string by using split extension function, size minus one gives you the occurence count.

you can test this solution on Kotlin Playground: https://pl.kotl.in/y6Sciwgzk

There seems to be no function from the standard library that counts substrings. But you can easily write an extension function that uses the indexOf(element, startIndex) function:

fun main() {
    val string = "5 kg rice 2 kg wheat 3 kg Soya"
    
    println(string.count("kg"))
}

fun String.count(element: String): Int {
    var count = 0
    
    // Check if the string contains the element at all
    var lastIndex = indexOf(element, 0)
    while (lastIndex >= 0) {
        count += 1

        // Find the next occurence
        lastIndex = indexOf(element, lastIndex + 1) 
    }
    
    return count
}