Find occurrences of a substring in a string in Kotlin

This article explores different ways to count the total number of occurrences of a string in another string in Kotlin.

1. Using `split()` function

In Kotlin, you can use the split() function to split the string around the given substring.

fun countMatches(string: String, pattern: String): Int {

return string.split(pattern)

.dropLastWhile { it.isEmpty() }

.toTypedArray().size - 1

}

fun main() {

val string = "AABCCAAADCBBAADBBC"

val pattern = "AA"

val count = countMatches(string, pattern)

println(count) // 3

}

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2. Using `Pattern.compile()` function

Another solution is to use regular expressions to count the substring frequency, as shown below:

import java.util.regex.Pattern

fun countMatches(string: String, pattern: String): Int {

val matcher = Pattern.compile(pattern).matcher(string)

var count = 0

while (matcher.find()) {

count++

}

return count

}

fun main() {

val string = "AABCCAAADCBBAADBBC"

val pattern = "AA"

val count = countMatches(string, pattern)

println(count) // 3

}

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3. Using `indexOf()` function

You can also write your custom routine solution using the indexOf() function, which returns the index within this string of the first occurrence of the specified substring. The trick is to start from the position where the last found substring ends. This would translate to a simple code below:

fun countMatches(string: String, pattern: String): Int {

var index = 0

var count = 0

while (true)

{

index = string.indexOf(pattern, index)

index += if (index != -1)

{

count++

pattern.length

}

else {

return count

}

fun main() {

val string = "AABCCAAADCBBAADBBC"

val pattern = "AA"

val count = countMatches(string, pattern)

println(count) // 3

}

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That’s all about finding the occurrences of a substring in a string in Kotlin.

Find occurrences of a substring in a string in Kotlin

1. Using split() function

2. Using Pattern.compile() function

3. Using indexOf() function

Share this:

1. Using `split()` function

2. Using `Pattern.compile()` function

3. Using `indexOf()` function