Kotlin Arrays (Lesson 9 PDF)

Kotlin is a statically typed programming language that runs on the Java Virtual Machine (JVM). It was developed by JetBrains and is now an official language for Android development. Kotlin is designed to be concise, expressive, and safe. It is also interoperable with Java, which means that you can use Kotlin and Java code together in the same project.

 Kotlin Arrays (Lesson 9 PDF)

Overview about the Lesson

In this lesson, we’ll cover the basics of Kotlin arrays, including how to create and initialize arrays, how to access and modify array elements, and how to traverse arrays.

The Content Of The Lesson

The lesson is divided into the following sections:

• Creating and initializing arrays
• Accessing and modifying array elements
• Traversing arrays
• Multidimensional arrays
• Array methods
• Array performance

Why This Lesson

Arrays are a fundamental data structure in programming, and Kotlin provides excellent support for working with arrays. By the end of this lesson, you’ll have a solid understanding of Kotlin arrays and how to use them in your programs.

Kotlin Arrays: Create, Access and Loop

The PDF introduces arrays step by step. Here are the operations you will use most, with their output.

Creating arrays

fun main() {
    val fruits = arrayOf("Apple", "Banana", "Cherry")
    val numbers = intArrayOf(5, 10, 15)
    val zeros = IntArray(4)               // [0, 0, 0, 0]
    val squares = Array(5) { i -> i * i } // [0, 1, 4, 9, 16]
    println(squares.joinToString())       // 0, 1, 4, 9, 16
}

Use intArrayOf, doubleArrayOf and friends for numbers: they avoid boxing and are faster than Array<Int>.

Reading and changing elements

fun main() {
    val fruits = arrayOf("Apple", "Banana", "Cherry")
    println(fruits[0])        // Apple (indexes start at 0)
    fruits[1] = "Mango"       // arrays have a fixed size but mutable elements
    println(fruits.size)      // 3
    println(fruits.last())    // Cherry
    println("Mango" in fruits) // true
}

Accessing an index that does not exist (fruits[3]) throws ArrayIndexOutOfBoundsException. Use getOrNull(3) when the index might be invalid.

Looping through an array

fun main() {
    val scores = intArrayOf(80, 95, 70)
    for (s in scores) println(s)
    for ((index, s) in scores.withIndex()) println("$index: $s")
    for (i in scores.indices) println(scores[i])
}

Useful array functions

Printing an array

println(fruits) prints something like [Ljava.lang.String;@1b6d3586, the array’s memory reference. Use fruits.joinToString() or fruits.contentToString() to print the elements.

Array or List?

Arrays have a fixed size. If you need to add or remove items, use a MutableList (mutableListOf("a","b")), which most Kotlin code prefers. Arrays are mainly used for performance-sensitive code, for main(args) and when calling Java APIs.

Practice exercise

Find the average of five test scores and count how many are above 75.

fun main() {
    val scores = intArrayOf(68, 82, 91, 74, 77)
    println(scores.average())             // 78.4
    println(scores.count { it > 75 })     // 3
}

Frequently Asked Questions

How do I compare two arrays in Kotlin?

a == b compares references, not contents. Use a.contentEquals(b) to compare elements.

Can a Kotlin array hold different types?

An Array<Any> can, but it is rarely a good idea. Prefer a data class or a list of a single type.

Continue the course

← Previous: Lesson 8: When, While, Break & Continue  |  Next: Lesson 10: For Loops & Ranges →

1. Lesson 1: Getting Started
2. Lesson 2: Syntax & Output
3. Lesson 3: Comments & Variables
4. Lesson 4: Data Types
5. Lesson 5: Operators
6. Lesson 6: Set Operations & Grouping
7. Lesson 7: Booleans & If…Else
8. Lesson 8: When, While, Break & Continue
9. Lesson 9: Arrays (you are here)
10. Lesson 10: For Loops & Ranges
11. Lesson 11: Functions & Classes
12. Lesson 12: Classes, Objects & Constructors
13. Lesson 13: Class Functions & Inheritance

Conclusion

In this blog post, we’ve covered the basics of Kotlin arrays, including how to create and initialize arrays, how to access and modify array elements, and how to traverse arrays. We’ve also explored some advanced topics, such as multidimensional arrays, array methods, and array performance. With this knowledge, you’ll be well-equipped to work with arrays in your Kotlin programs.

Download From Link

You can download the lesson from the following link:

From Here