30 August 2023
Learning a new programming language opens up new possibilities for your career and lets you build different types of applications. Kotlin is a modern, concise language that runs on the Java Virtual Machine (JVM) and can be used for Android development, web backends, desktop applications, and more.
This step-by-step guide will walk you through the fundamentals of Kotlin from installation to building real projects, providing numerous code examples along the way. By the end, you'll have the skills to start creating applications with Kotlin as a beginner.
This article is part of our Kotlin Training Course.
Before we dive into learning Kotlin, let's understand what Kotlin is and why it's gaining popularity:
These features make Kotlin a modern, improved alternative to Java without introducing radical changes. Understanding Kotlin opens up opportunities for mobile and backend development roles.
To write and run Kotlin applications, the first step is to setup the Kotlin compiler and tools on your development machine:
You can install the Kotlin compiler directly from the Kotlin website. Downloads are available for macOS, Windows, Linux and other platforms.
Unzip the downloaded file to a directory on your system. Inside, you'll find the Kotlin compiler *.jar
file along with useful scripts and examples.
Add the bin
directory path to your system PATH to be able to invoke the compiler from anywhere.
IntelliJ IDEA is a popular Java IDE by JetBrains that works well for Kotlin development. Install the Kotlin plugin:
The plugin takes care of configuring Kotlin for your projects within IntelliJ.
If you prefer Eclipse, install the Kotlin plugin for Eclipse from the JetBrains plugin repository. This will enable Eclipse for Kotlin application creation.
With the compiler and IDE support installed, let's write our first Kotlin program!
Traditionally, the first program you write in a new language prints out "Hello World". Here is how to do this in Kotlin:
fun main() {
println("Hello World!")
}
Let's understand what's happening in this simple one-liner:
main()
is the entry point function. Kotlin executes code inside main()
.fun
declares a function in Kotlin.println()
prints out text to the console.;
) can be omitted when separating statements on newlines.To run the program, save it as hello.kt
and run:
kotlin hello.kt
You should see "Hello World!" print out. With that simple program, you've already grasped some Kotlin fundamentals like functions, printing, and syntax! Let's move on to understand the building blocks of the language more deeply.
In this section, we will cover the essential concepts including:
if
and when
for
and while
These concepts power most of the programs you'll build in Kotlin. Let's look at them one-by-one:
Use var
and val
keywords to declare mutable and read-only variables respectively:
var mutableVar = 0
val immutableVal = 1
Variables must be initialized at the time of declaration.
Kotlin supports the following commonly used data types:
For example:
val positiveNumber: Int = 5
val pi: Double = 3.14159
val letter: Char = 'A'
The if
statement checks a condition and executes different code blocks based on boolean evaluation:
val x = 5
if (x > 0) {
println("Positive")
} else if (x < 0) {
println("Negative")
} else {
println("Zero")
}
if
can be used as an expression that returns a value.
The when
statement is like switch
in other languages, executing different code blocks based on the value:
when(x) {
0 -> print("Zero")
in 1..10 -> print("Positive")
else -> print("Negative")
}
The for
loop iterates over ranges, arrays, collections and more:
for (num in 1..10) {
println(num)
}
for (i in array) {
println(i)
}
The while
loop executes code repeatedly as long as the condition is true:
var i = 0
while (i < 10) {
println(i)
i++
}
These essential language elements allow you to start solving programming problems in Kotlin. Next let's look at functions.
Like most languages, Kotlin supports functions to reuse code:
fun main() {
printNumber(5)
}
fun printNumber(x: Int) {
println("The number is $x")
}
Let's understand Kotlin function syntax:
fun
declares a functioncamelCase
x: Int
{}
return
is optional. The last statement is implicitly returned.Now you can write reusable logic using functions!
Along with functions, Kotlin supports classes and object-oriented programming:
class Person(val name: String, var age: Int)
fun main() {
val person1 = Person("Kate", 20)
println(person1.name) // Outputs "Kate"
person1.age = 21
println(person1.age) // Outputs 21
}
Key highlights of Kotlin classes:
class
keyword defines a classval
defines immutable properties, var
defines mutable propertiesClasses allow you to model real-world objects and entity relationships.
With the basics covered, let's build a simple command line app that takes user input, does a calculation, and displays output.
We'll build an app that calculates simple interest based on user input:
fun main() {
print("Enter principal: ")
val principal = readLine()!!.toDouble()
print("Enter interest rate: ")
val rate = readLine()!!.toDouble()
print("Enter number of years: ")
val years = readLine()!!.toInt()
val interest = principal * rate * years / 100
println("Simple interest = $interest")
}
This covers several concepts:
stdin
input using readLine()
toDouble()
and toInt()
$interest
You now have the ability to create complete Kotlin programs for real-world use cases!
This guide covered Kotlin fundamentals, but Kotlin has many more features you can learn:
You can dive deeper into each topic and keep growing your Kotlin skills!
Here are some resources to continue your Kotlin education:
The Kotlin community has published many high-quality resources that greatly simplify your learning process.
Congratulations, you now have a solid foundation in the Kotlin language! Here are some next steps:
Kotlin is a skill that will serve you well for both mobile and server-side development. As you learn and apply Kotlin, remember that becoming a proficient developer takes time and practice. Be patient with yourself, keep coding, and have fun!
Here are some common questions about getting started with Kotlin:
Should I learn Kotlin or Java first?
Kotlin is a great alternative to Java. Learning either first will enable picking up the other quickly. Kotlin has a gentler learning curve.
What IDE is best for Kotlin?
IntelliJ IDEA is excellent for Kotlin development thanks to built-in tooling support via the Kotlin plugin. Android Studio and Eclipse also work well.
Can I use Kotlin for frontend web development?
Kotlin can compile to JavaScript, enabling frontend development. Consider using Kotlin/JS frameworks like React or Angular.
Is Kotlin good for backend development?
Yes, Kotlin is great for server-side development. It runs on the JVM and can reuse Java libraries. Some popular frameworks are Spring Boot, Ktor and Vert.x.
What companies use Kotlin?
Many top tech companies use Kotlin including Google, Pinterest, Coursera, Netflix, Uber and Square. Its adoption continues to grow.
Kotlin is a modern, versatile programming language that makes development faster and more fun. This step-by-step guide walked you through the fundamentals of Kotlin syntax, object-oriented features, building applications and more.
With these Kotlin basics, you can start tackling real projects. Kotlin has a gentle learning curve while teaching you skills that apply anywhere Java is used. The language improves developer productivity and makes creating applications safer.
Now that you have a Kotlin foundation, you can constantly build on it through practice, taking courses, joining communities and exploring frameworks. Your journey to learn Kotlin has just begun!
Check out our next article on Kotlin for Advanced Programmers: Take Your Skills to the Next Level
In the contemporary landscape of dynamic infrastructure environments, Kotlin emerges as an indispensable asset for both operations teams and developers. Its capacity to eloquently define, create, and manage infrastructure as code establishes a foundation for enhanced efficiency and collaborative infrastructure administration.
Whether initiating an exploration of infrastructure-as-code or enhancing an existing Kotlin-based setup, our comprehensive training modules at JBI Training stand ready to facilitate your mastery of this robust framework. Delay no more; adopt the prowess of infrastructure-as-code to revolutionize your infrastructure workflows without delay.
Initiate your educational journey now with the Kotlin courses at JB International and unlock the boundless potential of infrastructure-as-code at your disposal. Our offerings include:
Enrol in these courses and embark on a transformative journey to harness the power of Kotlin and infrastructure-as-code. Empower yourself to create, manage, and optimise digital infrastructures with confidence and expertise.
CONTACT
+44 (0)20 8446 7555
Copyright © 2024 JBI Training. All Rights Reserved.
JB International Training Ltd - Company Registration Number: 08458005
Registered Address: Wohl Enterprise Hub, 2B Redbourne Avenue, London, N3 2BS
Modern Slavery Statement & Corporate Policies | Terms & Conditions | Contact Us