Kotlin Sequence elementAtOrElse Function

The elementAtOrElse function in Kotlin is used to retrieve an element at a specified index in a sequence or return a default value if the index is out of bounds. It is part of the Kotlin standard library and provides a way to access elements based on their position within a sequence while handling out-of-bounds scenarios gracefully.

Table of Contents

1. Introduction
2. elementAtOrElse Function Syntax
3. Understanding elementAtOrElse
4. Examples
   • Basic Usage
   • Retrieving an Element in a Sequence of Strings
   • Using elementAtOrElse with Custom Objects
   • Chaining elementAtOrElse with Other Functions
5. Real-World Use Case
6. Conclusion

Introduction

The elementAtOrElse function allows you to access an element at a specified index in a sequence or return a default value if the index is out of bounds. This is useful for scenarios where you need to safely retrieve elements based on their position, avoiding IndexOutOfBoundsException.

elementAtOrElse Function Syntax

The syntax for the elementAtOrElse function is as follows:

fun <T> Sequence<T>.elementAtOrElse(index: Int, defaultValue: (Int) -> T): T 

Parameters:

• index: The index of the element to retrieve from the sequence.
• defaultValue: A lambda function that returns a default value if the index is out of the range of the sequence.

Returns:

• The element at the specified index or the default value if the index is out of bounds.

Understanding elementAtOrElse

The elementAtOrElse function works by iterating through the sequence until it reaches the specified index. If the index is within bounds, it returns the element at that index. If the index is out of bounds, it calls the defaultValue function and returns the result.

Examples

Basic Usage

To demonstrate the basic usage of elementAtOrElse, we will create a sequence of integers and retrieve an element at a specific index with a default value if the index is out of bounds.

Example

fun main() { val numbers = sequenceOf(1, 2, 3, 4, 5) val element = numbers.elementAtOrElse(10) { -1 } println(element) // Output: -1 } 

Output:

-1 

Retrieving an Element in a Sequence of Strings

This example shows how to retrieve an element at a specified index in a sequence of strings with a default value if the index is out of bounds.

Example

fun main() { val names = sequenceOf("Arjun", "Bhaskar", "Chitra", "Deepak", "Esha") val element = names.elementAtOrElse(6) { "Unknown" } println(element) // Output: Unknown } 

Output:

Unknown 

Using elementAtOrElse with Custom Objects

You can use the elementAtOrElse function to retrieve an element at a specific index in a sequence of custom objects with a default value if the index is out of bounds.

Example

data class Person(val name: String, val age: Int) fun main() { val people = sequenceOf( Person("Arjun", 25), Person("Bhaskar", 30), Person("Chitra", 22), Person("Deepak", 28), Person("Esha", 26) ) val element = people.elementAtOrElse(10) { Person("Unknown", 0) } println(element) // Output: Person(name=Unknown, age=0) } 

Output:

Person(name=Unknown, age=0) 

Chaining elementAtOrElse with Other Functions

The elementAtOrElse function can be chained with other sequence functions to perform more complex operations before retrieving the element at a specific index with a default value if the index is out of bounds.

Example

fun main() { val numbers = sequenceOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10) val element = numbers.filter { it % 2 == 0 } .elementAtOrElse(10) { -1 } println(element) // Output: -1 } 

Output:

-1 

Real-World Use Case

Retrieving a Specific Product

In real-world applications, the elementAtOrElse function can be used to retrieve a specific product from a sequence of products based on its position, with a default value if the index is out of bounds.

Example

data class Product(val name: String, val price: Double) fun main() { val products = sequenceOf( Product("Laptop", 1000.0), Product("Smartphone", 600.0), Product("Tablet", 300.0), Product("Headphones", 150.0) ) val element = products.elementAtOrElse(5) { Product("Unknown", 0.0) } println(element) // Output: Product(name=Unknown, price=0.0) } 

Output:

Product(name=Unknown, price=0.0) 

Conclusion

The elementAtOrElse function in Kotlin provides used for accessing elements at a specified index in a sequence while handling out-of-bounds scenarios gracefully. By understanding and using the elementAtOrElse function, you can efficiently retrieve elements based on their positions in your Kotlin applications, ensuring that you can access specific elements according to your requirements while providing default values for out-of-bounds indices.