{"id":204589,"date":"2022-02-22T12:56:27","date_gmt":"2022-02-22T12:56:27","guid":{"rendered":"https:\/\/www.softwaretestinghelp.com\/?page_id=204589"},"modified":"2025-04-01T09:43:53","modified_gmt":"2025-04-01T09:43:53","slug":"kotlin-tutorial","status":"publish","type":"page","link":"https:\/\/www.softwaretestinghelp.com\/kotlin-tutorial\/","title":{"rendered":"Kotlin Tutorial: What is Kotlin Programming Language"},"content":{"rendered":"\n

This Kotlin tutorial explains what is Kotlin Programming Language, its features, fundamentals, and how to write your first program in Kotlin:<\/strong><\/p>\n\n\n\n

Kotlin is a modern language that is concise as well as safe. It also provides a lot of advantages in terms of getting rid of the dreaded Null Pointer Exception.<\/p>\n\n\n\n

Kotlin is developed and maintained by Jetbrains – the company that also owns and builds IDEs like Intellij, Android Studio, PyCharm, etc.<\/p>\n\n\n\n \n \n\n\n

Getting Started With Kotlin Language<\/h2>\n\n\n\n
\"Kotlin<\/a><\/figure>\n\n\n\n

List of Tutorials in This Kotlin Series<\/span><\/strong><\/p>\n\n\n\n

Tutorial #1:<\/strong> Kotlin Tutorial: What is Kotlin Programming Language [This Tutorial]<\/a>
Tutorial #2:<\/strong> How to Use Kotlin Companion Object [With Examples]<\/a>
Tutorial #3:<\/strong> Kotlin Conditional Statements: When, While, For Loop, If Else<\/a>
Tutorial #4:<\/strong> Kotlin Data Class: When and How to Use Data Class in Kotlin<\/a>
Tutorial #5:<\/strong> Kotlin: Enums, Interfaces, and Generics<\/a><\/p>\n\n\n\n

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Kotlin has become a lot more popular and has gained a lot of traction ever since Google announced Kotlin as an official development language for Android.<\/p>\n\n\n\n

In this tutorial, we will learn the Kotlin language, by understanding its important features, and getting our hands on writing a basic program in the supported editors.<\/p>\n\n\n\n

Official Website<\/strong>: Kotlin<\/a><\/strong><\/p>\n\n\n\n

Note on Kotlin Versions:<\/strong><\/span><\/p>\n\n\n\n

The latest stable version of the Kotlin release is version 1.5.0 (released on May 5, 2021)
To read more about the details of the release, refer to Kotlin’s official documentation here<\/a>.<\/p>\n\n\n\n

Features of Kotlin<\/h3>\n\n\n\n

#1) Type Inference: <\/strong>In Kotlin, explicit mention of type can be omitted and the Kotlin compiler takes care of assigning an appropriate type to the variable depending on the type of data assignment that\u2019s done.<\/p>\n\n\n\n

Please note, this is always valid if you still want to explicitly define the type. Let\u2019s understand this with the help of an example. In Kotlin, both the below INT declarations are valid.<\/p>\n\n\n\n

var x: Int = 5\nvar x = 5<\/pre><\/pre>\n\n\n\n
#2) Java Interoperability: <\/strong>Kotlin is fully interoperable with Java – This simply means that both your Kotlin and Java code is interchangeable and can run side by side.<\/p>\n\n\n\n
#3) Clean Syntax: <\/strong>Kotlin has a concise less verbose syntax, as opposed to other languages like Java which is more verbose. For example<\/strong><\/span> – the Kotlin code does not require semicolons, you don\u2019t need to specify return types if it’s a void type, etc.<\/p>\n\n\n\n
#4) Null Safety: <\/strong>In programming languages like Java, a lot of defensive code is written to ensure that NullPointerException is not occurring in the code.<\/p>\n\n\n\n
In Kotlin, a lot of this checking happens at the compile time itself. Whether or not a variable can hold NULL value or not, can be defined at the compile time itself.<\/p>\n\n\n\n
For Example:<\/strong><\/span><\/p>\n\n\n\n
\/\/ will not compile&amp;lt;\/em&amp;gt;\nvar x: Int = null<\/pre><\/pre>\n\n\n\n
The above will not compile because the INT data type is not NULLABLE. If we want the variable x to hold NULL values as well, then should the data type be changed to INT?<\/p>\n\n\n\n
var x: Int? = null\nx = 10<\/pre><\/pre>\n\n\n\n
Also, now all operations on the nullable variable would need to do a null check at the compile time itself.<\/p>\n\n\n\n
\/\/ does not compile - due to no null check\nprintln(x + 5)<\/pre><\/pre>\n\n\n\n
In order to perform a null check, you can call the safe<\/strong> operator (?) or the !! operator which can be used when we are sure that the variable that’s being used won\u2019t be null.<\/p>\n\n\n\n
var x: Int? = 10\nprintln(x!! + 5)<\/pre><\/pre>\n\n\n\n
In this case – it will return the result 15.<\/p>\n\n\n\n
var x: Int? = null\nprintln(x!! + 5)<\/pre><\/pre>\n\n\n\n
If x is null – it would throw a Null pointer exception.<\/p>\n\n\n\n
#5) Extension Functions:<\/strong> In Kotlin, you can add new functionalities to an existing class using Extension functions. In most languages for adding new functionality to an existing class, you would inherit the class in a separate class and add new functionality. In Kotlin this can be achieved using extension functions. It\u2019s added like a function to the class but is defined outside that class. For example, to define an extension method to String class<\/p>\n\n\n\n
fun String.firstExtensionFunction() : String = \"Extension string\"<\/pre>\n\n\n\n
The above code would add a function named firstExtentionFunction <\/em><\/strong>to the String class and could be used by all String objects within the class where the extension function is defined.<\/p>\n\n\n\n
Let\u2019s see how a String variable can call this function<\/strong><\/p>\n\n\n\n
var x = &amp;quot;Test String&amp;quot;\nprintln(x.firstExtensionFunction())<\/pre><\/pre>\n\n\n\n
\/\/Output\n\"Extension string\"<\/pre>\n\n\n\n
Kotlin Dependencies<\/h3>\n\n\n\n
Kotlin is supported by all major build tools, namely Maven, Gradle, and Ant, and has dependency libraries available for all of these.<\/p>\n\n\n\n
For using Kotlin with Maven – we can add the standard Kotlin library as a dependency.<\/p>\n\n\n\n
&amp;lt;dependencies&amp;gt;\n&amp;lt;dependency&amp;gt;\n&amp;lt;groupId&amp;gt;org.jetbrains.kotlin&amp;lt;\/groupId&amp;gt;\n&amp;lt;artifactId&amp;gt;kotlin-stdlib&amp;lt;\/artifactId&amp;gt;\n&amp;lt;version&amp;gt;1.4.0&amp;lt;\/version&amp;gt;\n&amp;lt;\/dependency&amp;gt;\n&amp;lt;\/dependencies&amp;gt;<\/pre><\/pre>\n\n\n\n
The version can be specified as appropriate.<\/p>\n\n\n\n
Similarly, for using Kotlin with the Gradle build system, we can specify the Kotlin implementation library and add the Kotlin plugin for targeting JVM code.<\/p>\n\n\n\n
Hence, in your build.gradle file<\/p>\n\n\n\n