Kotlin Array - sortWith() Function

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The Kotlin array sortWith() function is used to sort the element of an array in place according to the order specified by the comparator function.

This function also accepts two optional parameters: formIndex and toIndex, to sort the elements in the range according to the comparator.

A comparator is a function that returns 1, -1, or 0 depending on the comparison of the two variables passed to the function.

Exception

Following are the exception −

• IndexOutOfBoundsException − If fromIndex is less than zero or toIndex is greater than the size of this array

• IllegalArgumentException − If fromIndex is greater than toIndex.

Syntax

Following is the syntax of Kotlin array sortWith() function −

fun <T> Array<T>.sortWith(comparator: Comparator<in T>)

Parameters

This function accepts following parameters.

• formInfex − It represents start of the range (inclusive) to sort, 0 by default.

• toIndex − It represents end of the range (exclusive) to sort, size of this array by default.

Return value

This function does not returns any value. It modify the original array into sorted array.

Example 1

Following is a basic example to demonstrate the use of sortWith() function −

fun main(args: Array<String>){
   val arr = arrayOf<Int>(5, 3, 6, 7, 4)
   arr.sortWith(Comparator<Int>{ a, b ->
      when {
         a > b -> 1
         a < b -> -1
         else -> 0
      }
   })
   print("Sorted array: ")
   println(arr.joinToString())
}

Output

The above code generate following output −

Sorted array: 3, 4, 5, 6, 7

Example 2

Now, we create an array of string. We then use sortWith() function to sort the elements of an array in descending order −

fun main(args: Array<String>){
   val arr = arrayOf<String>("Daisy", "Rahul", "Aman", "Prajwalani")
   arr.sortWith(Comparator<String>{ a, b ->
      when {
         a < b -> 1
         a > b -> -1
         else -> 0
      }
   })
   println("Sorted array: " + arr.joinToString())
}

Output

Following is the output −

Sorted array: Rahul, Prajwalani, Daisy, Aman

Example 3

The below example creates a comparator to sort elements in descending order. We then use sortWith() function to sort elements of an array according to this comparator −

fun main(args: Array<String>) {
   val numbers = arrayOf(42, 10, 23, 89, 5, 34)

   // Display the original array
   println("Original array: ${numbers.joinToString(", ")}")

   // create a custom comparator to sort the array in descending order
   val descendingComparator = Comparator<Int> { a, b -> when {
      a < b -> 1
      a > b -> -1
      else -> 0 }       
   }

   // Sort the array using the custom comparator
   numbers.sortWith(descendingComparator)
    
   // Display the sorted array
   println("Sorted array with comparator:"+ numbers.joinToString())
}

Output

The above code produce following output −

Original array: 42, 10, 23, 89, 5, 34
Sorted array with comparator:89, 42, 34, 23, 10, 5