Kotlin Introduction

Kotlin is a modern programming language developed by JetBrains. Google adopted it as the preferred language for Android app development in 2017. Kotlin runs on the Java Virtual Machine (JVM), which means it works wherever Java works — on desktops, servers, and Android phones.

Why Kotlin Exists

Java has been around since 1995. Over time, developers noticed that writing Java code required a lot of repeated, verbose code just to do simple things. JetBrains built Kotlin to solve this problem. Kotlin does everything Java does, but with less code and fewer common mistakes.

What Makes Kotlin Different

Concise Code

Kotlin removes boilerplate code. Boilerplate means code you write over and over just to satisfy the language rules, not because it adds value. Here is a comparison:

// Java way (verbose)
public class Person {
    private String name;
    public Person(String name) { this.name = name; }
    public String getName() { return this.name; }
}

// Kotlin way (concise)
class Person(val name: String)

Both do the same thing. Kotlin uses one line. Java uses seven.

Safe by Default

One of the most common errors in Java is the NullPointerException. This happens when a program tries to use a variable that holds nothing (null). Kotlin prevents this from happening by forcing programmers to declare upfront whether a variable can be empty or not.

Interoperable with Java

Kotlin and Java understand each other. You can use Java libraries in a Kotlin project and call Kotlin code from Java. This means companies can adopt Kotlin gradually without rewriting everything.

Where Kotlin Is Used

Kotlin works in several environments:

• Android Development – Build mobile apps for Android phones and tablets.
• Server-Side Development – Build web servers and APIs using frameworks like Ktor and Spring Boot.
• Multiplatform Projects – Share code between Android, iOS, and web apps using Kotlin Multiplatform.
• Desktop Apps – Build desktop applications using Compose Multiplatform.

Kotlin vs Java: A Simple Diagram

┌─────────────────────────────────────────────────┐
│               JVM (Java Virtual Machine)        │
│                                                 │
│   ┌──────────────┐       ┌──────────────┐       │
│   │  Java Code   │       │ Kotlin Code  │       │
│   │  (.java)     │       │  (.kt)       │       │
│   └──────┬───────┘       └──────┬───────┘       │
│          │                      │               │
│          ▼                      ▼               │
│   ┌──────────────┐       ┌───────────────┐      │
│   │ Java Bytecode│       │Kotlin Bytecode│      │
│   └──────────────┘       └───────────────       │
│                ↓                ↓               │
│           Both run on the same JVM              │
└─────────────────────────────────────────────────┘

Kotlin compiles down to the same bytecode as Java. The JVM does not care which language you used to write the code.

Key Facts About Kotlin

• Created by: JetBrains
• First release: 2011
• Stable version 1.0: February 2016
• Official Android language: May 2017
• Open source: Yes, under the Apache 2.0 license
• File extension: .kt