Kotlin vs Java: Which is Better for Android Development? 2024 Comparison

The programming language that you choose for your Android app development can significantly impact the success of your project in the long run. The right programming language can enhance productivity, improve code quality, and ultimately lead to a better user experience. 

With countless options available, developers often find themselves at a crossroads, wondering which path to take. Among the options available, two programming languages stand out as the most popular contenders: Kotlin and Java.

But which one is better for Android app development from Kotlin and Java? Why is Kotlin among the best alternatives for Java? Why is Kotlin preferred over Java?

Here, we will compare Kotlin vs Java for Android development and know their respective advantages, performance characteristics, learning curves, and much more. It will help you get a clear understanding of which language aligns well with your mobile app development goals. 

Kotlin for Android App Development

Kotlin is a statically typed, modern, and highly expressive programming language that has gained significant popularity in the Android development community. Google officially endorsed it as a first-class language for Android app development in 2017.

Kotlin is designed to be concise, which means you can achieve the same functionality with less code compared to Java. Its expressive syntax makes code more readable and less prone to errors.

Why Use Kotlin for Android Development?

Android app development with Kotlin offers several benefits, including:

1. Interoperability with Java – Kotlin is fully interoperable with Java, meaning you can seamlessly use Kotlin and Java code within the same Android project. This makes it easy for developers to transition from Java to Kotlin gradually.

2. Modern Language Features – Kotlin includes modern language features such as lambdas, extension functions, data classes, and smart casts, which simplify Android app development and enhance code quality.

3. Official Android Support  – Kotlin is officially supported by Android Studio (the primary IDE for Android development), which means it’s easy to set up and use for Android projects.

4. Community and Libraries – Kotlin has a growing and active community of developers, and it benefits from a wide range of libraries and tools that enhance Android app development.

5. Performance  – Kotlin’s performance is on par with Java, and in some cases, it can even outperform Java due to its more concise nature.

6. Android KTX – Kotlin Android Extensions (Android KTX) is a set of Kotlin extensions that simplifies Android code, making it more idiomatic and concise.

7. Conciseness – Kotlin’s concise syntax allows developers to write less code, reducing boilerplate and making code more readable.

8. Null Safety  – Kotlin for Android development includes built-in null safety features, reducing the risk of null pointer exceptions, a common source of crashes in Android apps.

9. Smart Casts – Kotlin’s smart casts simplify type casting, reducing the need for explicit type checks and casts.

10. Data Classes – Kotlin provides data classes that automatically generate common methods like equals(), hashCode(), and toString(), streamlining the creation of model classes.

11. Lambdas – Language Kotlin supports concise lambda expressions, making working with higher-order functions and asynchronous programming easier.

12. Coroutines – Kotlin offers native support for coroutines, simplifying asynchronous programming and improving code readability.

Read More: Top Rated Kotlin Development Company.

Java for Android Development

Android primarily uses Java as its primary programming language. Here are some key aspects of Java for Android development:

Java was the original and official language for Android app development. It is a mature programming language that has a well-established ecosystem for development scenarios of different kinds, like web development, software development, game development, and more. 

Developers can find extensive libraries, frameworks, and tools to use Java for Android app development. 

Kotlin vs Java Features for Android App Development

Now, let’s compare the features of both languages to understand why Kotlin is better than Java when it comes to Android development:

Feature	Kotlin	Java
Conciseness	Concise syntax reduces boilerplate code.	More verbose syntax requires more code.
Null Safety	Built-in null safety reduces null pointer exceptions.	Null safety relies on manual checks.
Extension Functions	Supports extension functions for existing classes.	Lacks extension functions.
Smart Casts	Offers smart casts for safer type casting.	Requires explicit type checks and casts.
Data Classes	Provides data classes for automatic code generation.	Manual creation of model classes.
Lambdas	Supports concise lambda expressions.	Lambda expressions are available.
Coroutines	Offers native support for coroutines.	No native coroutine support (prior to Java 14).
Ecosystem and Libraries	Growing ecosystem with Kotlin-specific libraries.	Mature ecosystem with extensive libraries.
Wide Adoption	Adoption is increasing at a fast pace because of the benefits it offers.	Was the primary language for Android app development.
Performance	Faster performance than Java.	Good performance with bytecode optimization.
Community Support	Active community with resources and support.	Large and active Java developer community.
Cross-Platform	Can be used for cross-platform development.	Limited cross-platform support (via NDK).

Kotlin vs Java Performance

Among the most popular alternatives to Java, Kotlin offers several performance benefits. It is worth noting that both languages use the concept of bytecode compilation on Java Virtual Machine (JVM), meaning the performance characteristics are pretty similar.

However, there are some features in Kotlin that enhance the overall performance of Android apps when compared to Java.

For instance, the null safety features in Kotlin decrease the quantity of runtime exceptions, which aids in faster performance. Another aspect is the immutability of data structures in Kotlin, which is another reason for better performance. 

Below is a comparison of Java vs Kotlin performance to help you understand things better:

Performance Aspect	Java	Kotlin
Code Size	Code size can be slightly larger in Java due to verbosity.	Kotlin’s concise syntax leads to smaller code sizes.  It loads faster, especially on slower devices or networks.
Null Safety Impact	Java allows null references, which can lead to null pointer exceptions at runtime.	Kotlin’s null safety features reduce null pointer exceptions, improving app stability.
Concurrency	Java uses traditional multithreading, which can be error-prone.	Kotlin’s coroutines simplify asynchronous programming and lead to more efficient and responsive apps.
Interoperability	Full interoperability with Java allows seamless use of Java libraries and code.	Full interoperability with Java ensures access to the rich ecosystem of Java libraries and tools.
Garbage Collection	Both languages rely on the Android runtime’s garbage collection, which can impact app performance.	Performance considerations related to garbage collection are similar for both languages.
Startup Time	Similar startup times as both languages run on the Android runtime.	Kotlin’s smaller code size leads to slightly faster startup times.
Compilation Speed	Java tends to have faster compilation times.	Kotlin compilation times can be slightly slower due to additional language features.
Runtime Performance	Comparable performance in terms of execution speed and efficiency.	Comparable performance as both compile to bytecode for the Android runtime.

So, when it comes to raw runtime performance, there is usually no significant difference between Java and Kotlin for Android app development. Other factors such as code readability, maintainability, and developer productivity are often more important considerations when choosing between the two languages. 

Kotlin’s concise syntax and null safety features indirectly bring faster performance by improving code size and reducing the likelihood of runtime crashes.

Kotlin vs Java Learning Curve

• Kotlin Learning Curve:

Kotlin is known for its relatively gentle learning curve, especially for developers who are already familiar with Java. It was designed to be easy to pick up for Java developers.

If you already have experience with Java, you’ll find many concepts in Kotlin to be familiar, and you can often leverage your existing Java knowledge.

Kotlin’s concise syntax and modern features make code more readable, which facilitates the learning process.

• Java Learning Curve

Java is a well-established language with a steeper learning curve for newcomers, primarily due to its more verbose syntax and boilerplate code.

Developers who are new to Java may need more time to become proficient in the language and its idiosyncrasies.

Java’s strict type system and explicit declarations require a deeper understanding of object-oriented programming (OOP) concepts.

Kotlin Community and Ecosystem

• The Kotlin community has been rapidly growing and is considered vibrant and enthusiastic. 

• Kotlin has a dedicated website (kotlinlang.org) with extensive documentation, tutorials, and a blog, making it a valuable resource for developers.

• Forums and social media platforms like Stack Overflow, Reddit, and GitHub have active Kotlin communities where developers can seek help, share knowledge, and collaborate.

• There are Kotlin user groups and meetups in various cities, providing opportunities for in-person networking and learning.

• The availability of Android-specific libraries and tools for Kotlin has expanded significantly, and Kotlin has become a first-class language in the Android ecosystem.

Java Community and Ecosystem

• Java has one of the largest and most established developer communities in the world, with a deep and enduring history in Android development.

• There is an abundance of resources, tutorials, forums, and documentation available for Java, making it easy for developers to find solutions to their problems and stay updated on best practices.

• The broader Java community extends beyond Android development and encompasses a wide range of domains and platforms, contributing to the language’s longevity and vitality.

• Android Studio, the primary Integrated Development Environment (IDE) for Android development, provides excellent support for Java, including code generation, refactoring tools, and a visual layout editor.

Libraries and Tools Available for Kotlin

• Kotlin enjoys growing support from third-party libraries and tools specifically designed for Android development. Many popular Android libraries now offer Kotlin-friendly versions, and new libraries are often Kotlin-first or Kotlin-exclusive.

• Kotlin’s interoperability with Java ensures that developers can leverage the extensive Java libraries and tools available in the Android ecosystem seamlessly.

• Android KTX (Kotlin Extensions) is a set of Kotlin-specific extensions for Android that simplifies Android development by providing idiomatic Kotlin APIs.

Libraries and Tools Available for Java

• Java has an extensive library ecosystem that has been built over decades, covering a wide range of domains, including Android development.

• Android developers have access to a vast array of third-party libraries, frameworks, and tools that can be used with Java. Many of these libraries have been used successfully in countless Android projects.

• Android Studio and the Android Gradle build system provide excellent support for integrating Java libraries into Android projects, simplifying the process of adding external dependencies.

Interoperability Between Java and Kotlin in Android Development

Java and Kotlin are designed to work seamlessly together, allowing developers to write code in either language within the same Android project. This interoperability is a key feature and provides numerous benefits for transitioning between the two languages.

• Mixed Language Source Code: In an Android project, you can have both Kotlin and Java source files. They can reference and call each other without any issues.

• Java Libraries: Kotlin can directly use Java libraries, and vice versa. This means you can take advantage of the extensive Java library ecosystem in Kotlin projects and utilize Kotlin in existing Java projects.

• Null Safety: Kotlin’s null safety features extend to Java code, helping prevent null pointer exceptions when Kotlin code interacts with Java code that doesn’t have null annotations.

• Data Conversion: Kotlin provides tools for seamless data conversion between nullable and non-nullable types when interacting with Java.

• Gradual Transition: Interoperability makes it easier to transition from Java to Kotlin or vice versa in a gradual manner. You can start by writing new code in the desired language while keeping existing code intact.

• Leverage Existing Code: For projects with an existing codebase in Java, you can leverage Kotlin’s concise syntax, null safety, and modern features in new code, improving code quality without rewriting everything.

• Easier Adoption: Developers familiar with Java can gradually learn Kotlin without abandoning their Java skills. Kotlin’s interoperability ensures that Java expertise remains valuable.

• Access to Rich Ecosystems: Both languages can access each other’s ecosystems. Kotlin projects can benefit from the extensive Java library ecosystem, while Java projects can use Kotlin’s modern features and extensions.

• Improved Code Quality: Kotlin’s null safety and modern language features can lead to better code quality and fewer runtime errors, making your Android app more robust.

Popular Apps Built With Kotlin or Migrated From Java to Koltin

For the benefits Kotlin offers, a large number of Android apps built on Java have migrated to Kotlin over the years. Some parts or codebases of these apps might still be running in Java because of the interoperability, but Kotlin is the primary language used now.

Trello

Trello, a popular project management app, announced in 2019 that they had fully migrated their Android app from Java to Kotlin. They reported improved developer productivity and code readability as key benefits.

Pinterest

Pinterest is another notable app that embraced Kotlin for Android development. They started incorporating Kotlin into their Android app in 2017 and continued to do so as it gained popularity.

Evernote

Evernote, a widely used note-taking app, adopted Kotlin in 2017. They cited reasons such as concise code and enhanced safety features as motivations for the transition.

Uber 

While not a complete migration, Uber’s Android app started including Kotlin years back. They found Kotlin to be a valuable addition to their codebase, improving their development process.

Slack

Slack, a popular communication and collaboration app, started doing its Android app development with Kotlin in 2018. They mentioned that Kotlin’s null safety features were particularly beneficial in reducing crashes.

Coursera 

Coursera, the online learning platform, began incorporating Kotlin into their Android app in 2017. They found that Kotlin helped streamline their code and improve development efficiency.

Basecamp 3

Basecamp, a project management and team collaboration app, adopted Kotlin for its Android app development. They reported positive experiences with the language in terms of developer productivity.

AliExpress

AliExpress, the e-commerce platform, migrated part of its Android app to Kotlin. They noted that Kotlin’s concise syntax and null safety features were advantageous.

Future Trends and Industry Adoption

• Kotlin-First Approach 

Some prominent companies and startups have adopted a Kotlin-first approach, meaning they use Kotlin as the primary language for Android app development. This trend reflects the confidence in Kotlin’s modern features, developer-friendly syntax, and improved safety.

• Java Legacy

Java continues to be widely used in Android app development, particularly in apps with established codebases. 

• Coexistence

Interoperability between Kotlin and Java allows developers to use both languages within the same project. This coexistence is especially prevalent in apps undergoing a transition from Java to Kotlin.

• Google’s Kotlin Focus

Google has continued to promote Kotlin as the language of choice for Android development. Many official Android libraries and resources now have Kotlin support, reinforcing Kotlin’s position in the ecosystem.

Why is Kotlin Preferred Over Java? Final Verdict

Kotlin’s adoption in the Android development community has been on a steady rise since Google officially endorsed it as a first-class language for Android. 

Many new Android projects are now being started in Kotlin, and existing apps are gradually migrating to Kotlin.

Kotlin continues its growth and will eventually become the dominant language for Android development. Its modern features, null safety, and enhanced developer experience make it an attractive choice.

Java will persist in Android development for the foreseeable future due to the vast number of existing Java-based apps and libraries. Many developers will continue to maintain and update Java codebases.

Interoperability between Kotlin and Java will remain essential as many projects continue to use both languages. The ability to incrementally adopt Kotlin or integrate Kotlin features into existing Java code will continue to be valuable.

Both Google and JetBrains (the creators of Kotlin) will likely invest in further enhancing tooling support for Kotlin, making it even more attractive for developers.

Frequently Asked Questions