How to migrate from java to kotlin

You might be aware about the fact that Kotlin is taking its supremacy over Java in the last few years. Java though being the oldest player in the technology industry since 1996 has a support from wide variety of programmers and coders. But in 2017, something got changed and Kotlin got a huge support from Google. 

Google considered Kotlin as the official language for developing Android apps.  

Kotlin language is used by many big companies including Google, Kickstar, and Square. Though some programmers prefer to use Java in today’s world because they got acquainted with that language and have acquired specific skills in it.  

But there are some challenges associated with Java for developing android applications. To deal with such challenges, it is preferable to use Kotlin.  

If you are stuck in figuring out the path as to whether you should migrate from Java to Kotlin or not, then this blog is for you.  

In this blog, I will discuss about the challenges involved in using Java to develop Android applications and will do a quick walkthrough as how you can migrate from Java to Kotlin.  

Let’s first understand the difference between Java and Kotlin –  

Java  Kotlin  
1. In Java, you need to write more code to achieve some tasks  1. Kotlin requires less amount of code to perform specific operation  
2. Java follows an object-oriented programming language  2. Kotlin follows both procedural and object-oriented programming language  
3. Java contains a multi-threading feature which is required for running long tasks in background. Multi-threading feature in Java prevents the freezing of mobile screen while running long operations. 3. Kotlin contains “Coroutines” which is comparatively lighter than Threads. Because of this feature, it makes possible for Kotlin to run long tasks in background with less memory consumption.  
4. In Java, it is possible to assign null values to a variable  4. Kotlin does not allow to initialize any object with null value  
5. Java allows the coder /programmer to write some extra codes to implement Singleton objects  5. Kotlin provides you with a feature called “object” which means a single object stays throughout the app  
6. In Java, we need to design our parent class and subclass to build the required extension function  6.  Kotlin has its inbuilt extension function feature  
7. Java does not provide smart casting feature. You need to check your variables and its types to perform typecasting  7. Kotlin provides “Smart Casting” functionality. It is embedded with a feature called “Kotlin Compiler” which gives you warning before the time of execution as to whether the casting is possible or not  
8. You need Constructor, Getter and Setter to create model class for API response or request etc. For instance – Getter is needed for getting value. On the contrary, setter is needed for setting the value 8. Kotlin does not require any Getter, Setter or Constructor to generate model class as it provides something called the Data class. Use the keyword “data” before class and it will become your model class. 

What are the challenges associated with Java? 

Here are the few challenges that companies are facing while using Java as their programming language – 

  • Java is considered as a language of complex syntax as it contains verbose codes which decreases the readability of code It is somewhat time-consuming process for the coder to write long codes for performing any task.  
  • Java does not support Null safety so there might be the possibility of higher risk of runtime failure  
  • It becomes difficult to test and identify bugs in Java  
  • There are more coders involved in Java. Though Java has been in high usage for past years as some old programmers are used to that programming language.  
  • There is high level of code issues which affects the performance of an application. The reasons could be many. For example – There could be a bug in code constructs or the code could be inefficient to perform 
  • There is an issue of deadlocks in Java. Its multi-threading feature sometimes slow down or crashes the application  
  • When you add too much data in Java, there could be a possibility of memory leaks  
  • Java is lagging behind Kotlin for developing android apps when it comes to desktop UI (User Interface)  

In a nutshell, Kotlin is way too smarter than Java as it makes the development process much easier which in turn optimizes the whole coding process.  

How to migrate from Java to Kotlin for developing android applications?  

It might feel like a daunting task when it comes to migrating your Android app from Java to Kotlin Here are the few simple and quick steps that you can follow to level up the development of your Android apps.  

1. Firstly, you need to install Kotlin Plugin. To install Kotlin plugin, go to plugin option in Android Studio or IntelliJ IDEA. From there, search Kotlin and install it  

2. In this stage, you need to add Kotlin extension, gradle plugin and other necessary library packages on build.gradle file.  

3. After you add kotlin extension, it’s high time for you to update .java files to .kt There are approaches you can adopt for converting all your files from Java to Kotlin-  

  • The first approach is about writing the entire code manually by following Kotlin syntax and renaming the file into .kt 
  • The second approach provides you with an automated tool that allows you to convert Java code into Kotlin in a couple of seconds.  

Converting your Java files into kotlin using second approach will save your hours and let you smoothen your development process. There might be a less possibility of manual errors involved.  

4. If you are choosing the second approach for migrating from Java to Kotlin, then you can opt this feature by going to code section which is located in Android Studio toolbar. Now, click on the option “Code” and then Convert Java to Kotlin file” from the end of dropdown list.  

5. When you do the conversion from Java to Kotlin by using an automation tool then it could be the possibility that the code does not work perfectly as the converter tool might change the logic and syntax. For Instance – Java static classes could be changed to companion. The coder can fix it manually.  

How to use the same code of Java with Kotlin? 

It is quite easy to use the same code of Java in Kotlin. You can use Java code functions, frameworks and library in a Kotlin. If you want to use the old Java code and use it in your Kotlin project then you can do so.  


Q1. Is it easy to migrate from Java to Kotlin? 

Yes, it is easy to migrate from Java to Kotlin using 3 simple steps mentioned below- 
Install Kotlin Plugin 
Update build.Gradle  
Convert your Java files into Kotlin. You can do the conversion either manually or by using automated conversion tool  

Q2. Why convert Java to Kotlin? 

Java contains verbose codes which decreases the readability of code. However, Kotlin takes away complexity of code by writing few syntaxes to perform a certain task. Additionally, Kotlin contains few extra features that are largely supported by android studio. This makes the entire development process much smoother.  
Here are few reasons as to why need to migrate from Java to Kotlin – 
1. Kotlin is a concise programming language as compared to Java  
2. Kotlin reduces the amount of code  
3. It enhances productivity than Java  
4. It produces safer and reliable experience  
5. It provides better Programmer Experience  


Kotlin is though a new language for developing Android apps but Kotlin is future. Kotlin is considered as the google official language as it lowers the workload of a developer and improves the functionality of Android apps.  

There is always a war as to which language you should choose for Android development. But the fact is that whichever language you choose, your programmers must have a know how to operate it. There has been seen a rising trend in the growth of Kotlin and many developers are heading towards this.  

So, this guide provided you a walkthrough of how to migrate from Java to Kotlin and you got your answer now.  

If you have any questions regarding development of Android apps then you can contact us. Book a 40 min free discovery call with our Android experts to discuss about your project requirements. 

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