In this tutorial, you shall learn how to sort an array of strings based on their length in Kotlin, using Array.sortBy() method, with examples.

Kotlin – Sort array of strings based on length

To sort an Array of Strings based on its length property in Kotlin, use Array.sortBy() method. sortBy() method sorts the calling array in-place in ascending order based on the selector passed as argument.

Syntax

The syntax to call sortBy() method on Array arr is

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arr.sortBy(selector: (T) -> (R))

The selector function takes element as argument and returns a value which is used for comparison between elements.

Examples

In the following example, we take an array of strings, and sort them in ascending order in-place based on length using sortBy() method.

Main.kt

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fun main(args: Array<String>) {
    val arr = arrayOf("banana", "kiwi", "apple")
    val selector: (String) -> Int = { str -> str.length }
    arr.sortBy(selector)
    for (x in arr) print("$x  ")
}

Output

kiwi  apple  banana

We can also specify the selector function directly as shown in the following program.

Main.kt

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fun main(args: Array<String>) {
    val arr = arrayOf("banana", "kiwi", "apple")
    arr.sortBy { it.length }
    for (x in arr) print("$x  ")
}

Output

kiwi  apple  banana

Conclusion

In this Kotlin Tutorial, we learned how to sort a String Array based on string length using sortBy() method, with examples.