Differences Between Java and Kotlin

by

When it comes to choosing a programming language for app development, two popular options often come up in discussions: Java and Kotlin. Both languages have their own strengths and weaknesses, and understanding the differences between them is crucial for developers looking to create high-quality apps. In this article, we’ll delve into the world of Java vs Kotlin, exploring the key differences between these two programming languages that are widely used in Android development. From syntax and semantics to performance and ecosystem, we’ll break down the pros and cons of each language, let’s start with a brief summary of each language.

Java

Java is a general-purpose, class-based, object-oriented programming language designed with the principle of “Write Once, Run Anywhere.” It runs on the Java Virtual Machine (JVM) and has been a dominant enterprise language for over two decades.

Kotlin

Developed by JetBrains in 2011 and officially released in 2016, Kotlin is a modern, cross-platform programming language designed to interoperate fully with Java while addressing many of its limitations. Google announced Kotlin as the preferred language for Android development in 2019.

Key Differences

Java vs Kotlin some of the key differences are:

  1. Null Safety
  • Java: Allows null assignments leading to potential NullPointerExceptions
  • Kotlin: Built-in null safety with nullable and non-nullable types
// Kotlin
var nullable: String? = null     // Allowed
var nonNullable: String = "text" // Can't be null
  1. Smart Casts
  • Java: Requires explicit casting
  • Kotlin: Automatically casts after type checks
// Kotlin
if (object is String) {
    print(object.length) // Automatically cast
}
  1. Extension Functions
  • Java: Utility classes needed
  • Kotlin: Can add methods to existing classes
// Kotlin
fun String.addHello(): String = "Hello $this"
  1. Data Classes
  • Java: Requires boilerplate code for POJOs
  • Kotlin: One-line class definition
// Kotlin
data class User(val name: String, val age: Int)
  1. Coroutines
  • Java: Thread-based concurrency
  • Kotlin: Lightweight coroutines for async programming
// Kotlin
launch {
    delay(1000)
    println("Coroutine completed")
}

Detailed Comparison

Syntax and Readability

  1. Semicolons
  • Java: Required
  • Kotlin: Optional
  1. Type Inference
  • Java: Limited type inference
  • Kotlin: Comprehensive type inference
// Kotlin
val list = mutableListOf("item") // Type inferred
  1. Expression Bodies
  • Java: Requires full method syntax
  • Kotlin: Single-expression functions
// Kotlin
fun double(x: Int) = x * 2

Safety Features

  1. Immutability
  • Java: Mutable by default
  • Kotlin: Distinguishes between val (immutable) and var (mutable)
  1. Platform Types
  • Java: No distinction for nullable types from other languages
  • Kotlin: Special handling for Java interop types

Functional Programming

  1. First-class Functions
  • Java: Limited support before Java 8
  • Kotlin: Full support with function types
  1. Lambda Expressions
  • Java: Verbose syntax
  • Kotlin: Concise syntax with implicit parameters
// Kotlin
list.filter { it > 10 }

Use Cases

Java

  • Enterprise Applications
  • Large-scale Backend Systems
  • Android Development (Legacy)
  • Web Services
  • Financial Systems

Kotlin

  • Android Development (Preferred)
  • Server-side Applications
  • Multiplatform Projects
  • Modern Web Applications
  • DSL Creation

Future Perspective

Java

  1. Evolution
  • Project Loom: Lightweight threads
  • Project Valhalla: Value types
  • Pattern matching enhancements
  • Records and sealed classes improvements
  1. Market Position
  • Continued enterprise dominance
  • Growing competition in mobile development
  • Strong in microservices architecture

Kotlin

  1. Growth Areas
  • Multiplatform development expansion
  • Increased server-side adoption
  • Growing DSL capabilities
  • Enhanced coroutines features
  1. Future Developments
  • Improved compilation speed
  • Enhanced multiplatform support
  • Better tooling integration
  • Expanded standard library

Industry Adoption

Java

Kotlin

Conclusion

While Java maintains its position as the enterprise standard, Kotlin’s modern features and Android focus make it increasingly popular. The languages’ interoperability allows organizations to migrate gradually, choosing the best tool for specific use cases while maintaining existing codebases.