How to Slice List in Kotlin: Syntax and Examples

In Kotlin, you can slice a list using the slice() function with a range or a list of indices. For example, myList.slice(1..3) returns a new list with elements from index 1 to 3.

Syntax

The slice() function extracts elements from a list based on specified indices or ranges.

• list.slice(indices: Iterable<Int>): Returns a new list with elements at the given indices.
• list.slice(range: IntRange): Returns a new list with elements in the specified index range.

Indices start at 0, and the original list is not modified.

kotlin

val myList = listOf("a", "b", "c", "d", "e")

val sliceByRange = myList.slice(1..3)  // elements at indices 1, 2, 3
val sliceByIndices = myList.slice(listOf(0, 2, 4))  // elements at indices 0, 2, 4

Example

This example shows how to slice a list using both a range and a list of indices. It prints the sliced lists to demonstrate the output.

kotlin

fun main() {
    val fruits = listOf("Apple", "Banana", "Cherry", "Date", "Elderberry")

    val sliceRange = fruits.slice(1..3)  // Banana, Cherry, Date
    val sliceIndices = fruits.slice(listOf(0, 2, 4))  // Apple, Cherry, Elderberry

    println("Slice by range (1..3): $sliceRange")
    println("Slice by indices (0, 2, 4): $sliceIndices")
}

Output

Slice by range (1..3): [Banana, Cherry, Date]
Slice by indices (0, 2, 4): [Apple, Cherry, Elderberry]

Common Pitfalls

Common mistakes when slicing lists in Kotlin include:

• Using indices out of the list's bounds, which throws an IndexOutOfBoundsException.
• Confusing slice() with subList(). slice() creates a new list, while subList() returns a view.
• Using ranges that are empty or reversed, which results in an empty list.

kotlin

fun main() {
    val numbers = listOf(10, 20, 30, 40, 50)

    // Wrong: index 5 does not exist (list size is 5, max index 4)
    // val wrongSlice = numbers.slice(2..5)  // Throws exception

    // Right: use valid range
    val rightSlice = numbers.slice(2..4)  // 30, 40, 50

    println("Valid slice: $rightSlice")
}

Output

Valid slice: [30, 40, 50]

Quick Reference

Operation	Syntax	Description
Slice by range	list.slice(startIndex..endIndex)	Returns elements from startIndex to endIndex inclusive.
Slice by indices	list.slice(listOf(index1, index2))	Returns elements at specified indices.
Sublist (view)	list.subList(startIndex, endIndex)	Returns a view from startIndex (inclusive) to endIndex (exclusive).
Index out of bounds	list.slice(invalidRange)	Throws IndexOutOfBoundsException if indices are invalid.

Key Takeaways

Use slice() with ranges or lists of indices to get parts of a list in Kotlin.

Indices start at 0 and must be within the list size to avoid errors.

slice() returns a new list; it does not modify the original list.

Avoid using invalid or reversed ranges to prevent empty results or exceptions.

For a view instead of a copy, consider subList() with exclusive end index.