Java to Kotlin

migrate your old app code to the new territories

Java to Kotlin conversion

Your Java mobile app project might have been created some time ago and it might seem difficult to develop it further due to cluttered and not very transparent coding.

We believe that converting your Android app from Java to Kotlin will allow you to expand your app with new features while keeping a neat and orderly coding environment at the same time.

java logo
kotlin logo

Here are some facts to prove that converting Java to Kotlin is a good idea


Kotlin introduces data keyword for classes. It basically has the same purpose as the Java model class, but the number of lines needed to achieve it is incomparably lower. All variants of constructors, getters and setters methods are declared on the top of a class, thanks to this your data class can an one-liner.


It allows to declare default arguments which makes overloading of the methods in one declaration, no need for boilerplate code as it is in Java.


It has got great mechanisms for making code reusable, extension functions can be created for any objects, including Java classes.


It provides a null-safety coding environment, which keeps infamous Java NullPointerException just a memory of the past.

Read more about this on our blog:

Is Kotlin better than Java?

Code in Java

print screen of class declaration in java

Code in Kotlin

print screen of class declaration in kotlin

Kotlin creates a more readable and lightweight wireframe for developing new features without excessive amount of work and creating spaghetti monsters. Current predictions are that within a year all Android Apps will be written in Kotlin - it is simply easier and faster.

Our job on a project


Evaluating the quality of the existing code


Building rationale for converting from Java to Kotlin


Basing the new code on an existing project in order to guarantee app continuity on Google Play


Code rewriting in batches to make sure all app functionality is covered - piece after piece continuity on Google Play


Updates with new parts of code rewritten to Google Play continuously without any interference in user experience

Benefits for your organisation


Better time to market - faster reaction to current trends


Better code quality


Quicker and smoother onboarding of new devs


Faster implementation of unit tests and easier testing


Better exchange in information between Android and iOS interference in user experience

Tools we use

intellij idea logo

IntelliJ IDEA for quicker and easier programming. It gives developer better coding experience providing various tools for debugging, autocompletion and refactoring.

android studio logo

It's Google supported IDE for creating Android applications, we stay updated with latest releases which allows us to make better apps.

zeplin logo

We use Zeplin as a bridge between UI/UX designers and developers, helps us to have mock insight of how the end product should look like.

atlassian logo

We use tools from Atlassian like JIRA for handling project flow, Confluence for documentation, Bitbucket for code version control and Pipeline to keep track of our releases. It helps us unify processes and have all data in one place related to each other.

Frequently Asked Questions

Is it better to use basic automatic converters for rewriting Java source files or to program in Kotlin from the scratch?

It depends on the complexity and actual condition of the project, some project will need writing from scratch in Kotlin, and for some refactor to Kotlin will be enough.

What is the best way to convert my Java file to Kotlin?

If you want to do this automatically we recommend to use IntelliJ IDEA or Android Studio where you can navigate to Code menu and then choose Convert Java File to Kotlin File option. Note that newly converted file have no .kt extension.

Is Kotlin better?

If we talk about Android it is true that applications for this platform can be written in several languages and can run on Java virtual machine. Kotlin is one of those languages, it is JVM compatible, and as it was designed to be better than Java with all its superpowers it's hard to find any better language for Android so far.

Is Kotlin Java compatible?

Yes, it's fully interoperable with Java. Kotlin creator put major efforts on making sure that the existing Java codebase can interact properly with Kotlin. Kotlin code can be easily called from Java and Java code from Kotlin.

If any of that seems interesting for you let us know!

Contact us