What is Kotlin and why is it used for Android?

Question

Accepted Answer

**Kotlin** is a modern, statically-typed programming language that is now **Google's preferred language for Android development**. It's concise, safe (null safety), interoperable with Java, and offers features that make Android development more productive and less error-prone.

## What Kotlin is

```text
Kotlin = a modern JVM language (by JetBrains), Google's PREFERRED language for Android:
  → concise, expressive, statically typed
  → 100% INTEROPERABLE with Java (use Java libraries; mix in a project)
  → "Kotlin-first" — Android APIs and docs favor Kotlin
```

## Key Kotlin features for Android

```kotlin
// NULL SAFETY — types are non-nullable by default (prevents NullPointerExceptions)
var name: String = "Ann"      // can't be null
var nickname: String? = null  // nullable (the ? allows null)
val len = nickname?.length    // safe call (null if nickname is null)

// CONCISE — data classes, type inference, less boilerplate
data class User(val name: String, val age: Int)   // auto equals/hashCode/toString/copy

// extension functions, lambdas, smart casts, coroutines (async), etc.
val doubled = list.map { it * 2 }   // concise functional style
```

## Why Kotlin over Java for Android

```text
✓ NULL SAFETY → eliminates many NullPointerExceptions (a top crash cause in Java apps)
✓ CONCISE → much less boilerplate than Java (data classes, no getters/setters, etc.)
✓ SAFER and more expressive; modern features (coroutines for async, extensions)
✓ COROUTINES → clean asynchronous programming (vs callbacks/threads)
✓ Google-recommended and Kotlin-first → best support, modern Android uses it
→ Interoperable with Java → adopt gradually; use existing Java code/libraries
```

## Why it matters

Understanding Kotlin and why it's used for Android is important because Kotlin is **Google's preferred, recommended language for Android development**, so it's essential foundational knowledge for modern Android work.

Kotlin is a modern, statically-typed JVM language that is now the **Kotlin-first** standard for Android (with Android APIs, documentation, and modern development favoring it), making it the language to know for current Android development.

Understanding its **key features** — especially **null safety** (types being non-nullable by default, preventing NullPointerExceptions, which were a top cause of crashes in Java Android apps — a significant reliability improvement), **conciseness** (data classes, type inference, and far less boilerplate than Java), and modern features (extension functions, lambdas, smart casts, and **coroutines** for clean asynchronous programming) — is necessary for writing modern Android code and explains why Kotlin is preferred.

Understanding **why Kotlin over Java** (null safety eliminating a major crash source, conciseness reducing boilerplate, safer and more expressive code, coroutines for clean async, Google's recommendation, and Java interoperability allowing gradual adoption and use of existing Java code) reflects the real benefits driving Kotlin's adoption.

Since Kotlin is the recommended, Kotlin-first language for modern Android development (essential to know for current Android work) and understanding its features (especially null safety and conciseness) and advantages over Java is necessary for writing modern Android apps, understanding Kotlin and why it's used for Android is essential, foundational knowledge for Android development — the language of modern Android, necessary for writing current Android code and understanding why it's preferred, a baseline requirement for Android developers today.