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Java vs. Kotlin: Which One To Pick While Building An Android App?

Oct 21, 20205 min read

Miłosz Kaczorowski

Co-founder at Ideamotive. Technological advisor and software consultant.

So you got an idea of the mobile app. Every great idea needs a tool to be made. In this article we are going to compare 2  tools: Java and Kotlin. You will see the strengths and weaknesses of each, and decide if Java or Kotlin will fit your goals. Earlier we made an ultimate article about Flutter app development, you can check it out after reading this one.


In this ultimate comparison of Java vs. Kotlin, you will find the following information:

  • What is Java?
  • What is Kotlin?
  • Comparison:
    • Speed of coding
    • Performance 
    • Stability
    • Documentation
    • Popularity 
    • Community
    • Talent pool 
    • Easiness to learn
  • Brief Comparison Table of Java vs. Kotlin
  • What is Java good for? + Examples
  • What is Kotlin good for? +Examples

Android Development Business Guide

What is Java?

Java is an object-oriented programming language. It was released in 1995 by Sun Microsystems. This company is the property of Oracle. Most Java elements are available in open-source. 


A large part of the Android apps and the Android itself are based on Java. In 2021 Java is the 4th most popular language as per the 2021 StackOverflow Dev Survey. Developers of all kinds use it to build the following:

  • Android apps;
  • Web apps;
  • Embedded systems;
  • Big Data tools and systems;
  • Server apps, and more.

What is Kotlin?

Guys from JetBrains launched Kotlin to make coding in Java more productive. Kotlin became an official programming language in 2018. It is the programming language that runs on JVM. JVM means Java Virtual Machine. Besides that, Kotlin can be compiled into JavaScript and run in browsers. It is possible to code on Kotlin/Native. Android developers can use IDE to build cross-platform apps. 


Most tech giants make their Android apps with Kotlin. Others are planning the migration. While we say enterprise leaders, we mean the companies like:

  • Netflix;
  • Trello;
  • Pinterest;
  • Uber;
  • Twitter.

Kotlin vs. Java  — An Ultimate Comparison With Examples

In this part of the article, we will compare Java and Kotlin programming languages in terms of the parameters important for the development. They include the following:

  • Speed of Coding;
  • Performance;
  • Stability;
  • Documentation;
  • Popularity;
  • Community;
  • Talent Pool;
  • Easiness to Learn.

Speed Of Coding

We can say that Java and Kotlin have the same speed of coding. Kotlin has more laconic constructions that allow a coder to type less. Yet, there is a trick. Finding a solution to a task on Kotlin needs more time than on Java. That means Kotlin has more cognitive load than Java. If you are a fantastic abstract thinker, Kotlin is your choice.


If you choose Java, you have to type more code than in Kotlin. We are talking about the process of the solution of the same task. Yet, you will spend less time thinking of the solution using Java than Kotlin. 


This doesn’t make a noticeable difference. We can say that the speed of coding on Java and Kotlin is the same.


Verdict: draw

Kotlin vs. Java Performance 

This parameter is too opinionated. Both Kotlin and Java compile to ByteCode that runs on JVM. It’s nearly impossible to compare Kotlin vs. Java when it comes to memory usage. So it's hard to measure, track, and compare their performance, but we will try.


Kotlin is more functional than Java. It has more extra features than Java. Kotlin is more convenient to work with multithreading apps. It's true because of the Coroutines tool Kotlin has. Yet, Kotlin compiles and executes a little slower than Java. It happens because of the vast number of features Kotlin has.


Java has less extra features than Kotlin and is a little simpler. But due to this fact, it compiles faster than Kotlin. It works a little quicker than Kotlin due to the absence of extra features.


But this difference is not generally noticeable and varies. We can say that Java and Kotlin have the same performance.


Verdict: draw


Stability is the parameter where we can see the difference. Let’s start with Java. This language has existed for quite a long time. It has versions with long-term support, like Java 8 and Java 11. What is long-term support? If anything goes wrong with these versions, devs fix it with a patch. Following this link, you can download different versions of Java with a free license.


We can call Kotlin quite an established object oriented programming language, but it is younger than Java. There are no versions with long-term support. In general, we can call both Java and Kotlin stable languages. But if stability is your main priority, it’s best to choose Java.


Verdict: Java

Kotlin vs. Java Documentation (With Examples)

Both Java and Kotlin have enough documentation to learn. Java has existed longer than Kotlin, so it's easy to find a tutorial or a book. Developers consider Java as the most straightforward programming language to learn. Here you can find some official Java documentation from Oracle.


Kotlin is a comparatively young language, yet, it has enough good official docs. It would help if you dug a little deeper to find some trusted sources on Kotlin. But that's it, no more difference.


Verdict: draw

Kotlin vs. Java Popularity Comparison (With Examples)

According to Google Trends, Java awakes much more interest than Kotlin. Java has been through some ups and downs. But Kotlin is not even close to the popularity of Java.


Java vs. Kotlin- Which One To Pick While Building An Android App? - google trends

Source: Google Trends.


We can assume this happens because Java exists for longer. Another reason is that Java needs less cognitive investments in learning.


Java vs Kotlin Which One To Pick While Building An Android App? - dzone

Source: DZone


Java and Kotlin are similar and different at the same time. And Java is here for more time. That’s why the difference in their popularity is so visible.


Verdict: Java


Since Kotlin comes from Russia, many Russian developers switched to this language. Russian people form the core of the Kotlin community. Look at Google Trends above. You’ll see Kotlin’s squad is around 20 times smaller than Java’s.


The Java community has many people from India. Java is quite simple to learn, and India got many junior devs. So they start with learning Java. Its squad is large. So if you face any issue, there is a high chance someone resolved it before.


Verdict: Java

Talent pool 

The latest Dev Survey shows that Kotlin is within the most popular techs. (Source: StackOverflow Dev Survey). 9.09% of pro developers choose this language. Java is chosen by 34.51%.


Kotlin brings more money to the devs than Java. Kotlin brings $55K per year, while Java brings $51K. (Source: StackOverflow Dev Survey).

You don’t need a developer in your office to make a cool product. So we take global rankings data for this part of the article.

Verdict: Kotlin

Kotlin vs. Java: Which One Is Easier To Learn?

Java is a little easier to learn than Kotlin. You need to write more code in Java than in Kotlin to resolve the task. But Java exists longer, so you will find tutorials easier. It’s easy to find proper docs and ready-made solutions on Java. 


Kotlin needs more cognitive investments in learning than Java. But it allows for resolving the same problems with less code than Java. If you are a good abstract thinker, learning Kotlin won’t be an issue for you. 


Verdict: Java

Brief Comparison Table Of Java vs. Kotlin

Java vs Kotlin Which One To Pick While Building An Android App - comparison table

Kotlin vs. Java. When to Use & Examples:

Let's switch to the practical part of Java and Kotlin's usage. These programming languages are similar, but devs use them for different tasks. Below you will find out what technology is best for your project. And the answer to the main question: Java vs. Kotlin for Android development — what is better?


What is Java good for? (+ a few examples)


Java is a universal language. Ten years ago, people used it to build some Android apps. But now it has found a use for BigData, eCommerce, and enterprise systems. There are popular instruments for BigData like Hadoop and HBase. Hadoop contains MapReduce and HDFS, as well as tech giants, use Java for their high-loaded servers. 


Companies use Java to develop enterprise systems. There are BPM and Rule Engines. JakartaEE offers many services for enterprises; also, e-commerce companies use Java.



  • Netflix;
  • Apple TV;
  • Hybris;
  • ATG.

What is Kotlin good for? (+ a few examples)


Companies and indie developers use Kotlin to develop Android applications. Almost every app in the Google Play Market has Kotlin as a base. Kotlin serves as a base of writing microservices. So Kotlin is better for Android when it comes to modern mobile app development. In this case, it is combined with Spring Boot, Quarkus, and Micronaut.



  • Pinterest;
  • Coursera;
  • Trello;
  • Evernote.

The Bottom Line

For Android development, Kotlin seems to be the best option at the moment. Many companies and developers are adopting it, and the language is likely to continue to evolve.


However, Java remains a great general-purpose language. Plus, it has been an Android favorite for a long time, so it's not that quick to replace it.


In conclusion, the debate over which language is the best is not straightforward and will likely lead to exciting discussions. Moreover, there are more aspects to consider than just language differences, such as the language companies use and how comfortable developers feel with Kotlin or Java.


It’s up to you which technology to go with. In turn, we can provide you with seasoned Java and Kotlin developers matched with your industry and goals.


Want to make the right decision? Let us know, we will help you.

Miłosz Kaczorowski

Co-Founder of Ideamotive. Highly skilled in Ruby on Rails, JavaScript and Linux System Administration. Experienced in implementing effective web apps.

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