Kotlin subList Function | Get Sub-list of List in Kotlin

The subList function in Kotlin is used to create a view of a specified range within a list. This function belongs to the List interface in the Kotlin standard library and allows you to work with a portion of the list without modifying the original list.

Table of Contents

1. Introduction
2. subList Function Syntax
3. Understanding subList
4. Examples
   • Basic Usage
   • Modifying the Sublist
   • Using subList in a Real-World Scenario
5. Conclusion

Introduction

The subList function provides a way to create a view of a specified range within a list, enabling you to work with a subset of the list elements. This is particularly useful for operations that need to be performed on a segment of the list.

subList Function Syntax

The syntax for the subList function is as follows:

fun <T> List<T>.subList(fromIndex: Int, toIndex: Int): List<T>

Parameters:

• fromIndex: The start index (inclusive) of the sublist.
• toIndex: The end index (exclusive) of the sublist.

Returns:

• A view of the specified range within the list.

Understanding subList

The subList function returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive. The returned list is backed by the original list, so changes in the sublist are reflected in the original list.

Examples

Basic Usage

To demonstrate the basic usage of subList, we will create a sublist from an existing list.

Example

fun main() {
    val numbers = listOf(1, 2, 3, 4, 5, 6, 7)
    val subList = numbers.subList(2, 5)
    println("Original list: $numbers")
    println("Sublist: $subList")
}

Output:

Original list: [1, 2, 3, 4, 5, 6, 7]
Sublist: [3, 4, 5]

Modifying the Sublist

This example shows how modifications to the sublist are reflected in the original list.

Example

fun main() {
    val numbers = mutableListOf(1, 2, 3, 4, 5, 6, 7)
    val subList = numbers.subList(2, 5)
    println("Original list: $numbers")
    println("Sublist: $subList")

    subList[0] = 99
    println("Modified sublist: $subList")
    println("Modified original list: $numbers")
}

Output:

Original list: [1, 2, 3, 4, 5, 6, 7]
Sublist: [3, 4, 5]
Modified sublist: [99, 4, 5]
Modified original list: [1, 2, 99, 4, 5, 6, 7]

Using subList in a Real-World Scenario

This example demonstrates how to use subList in a real-world scenario, such as processing chunks of data.

Example

fun main() {
    val data = listOf("A", "B", "C", "D", "E", "F", "G", "H")
    val chunkSize = 3
    val chunks = mutableListOf<List<String>>()

    for (i in data.indices step chunkSize) {
        val end = (i + chunkSize).coerceAtMost(data.size)
        chunks.add(data.subList(i, end))
    }

    println("Data chunks: $chunks")
}

Output:

Data chunks: [[A, B, C], [D, E, F], [G, H]]

Conclusion

The subList function in Kotlin's List interface is a useful method for creating a view of a specified range within a list. It allows you to work with portions of a list efficiently and can be used in various scenarios, including data processing and segmenting lists for operations.