Kotlin vs. Java: Which is the Winner?

Kotlin vs. Java’s battle is like a boxing match where a young and ambitious contender tries to take the title from a mature and experienced but old champion. And as we advance, the winner is already determined—the bout for the best Android development programming language between Java vs. Kotlin ended in a unanimous decision for the new contender. 

More and more modern companies and developers worldwide prefer young Kotlin for Android app development. This did not begin yesterday—in 2017, Kotlin became the second official programming language for the Android platform, and it was already in the middle of the path. Let’s find out the reasons why Java lost its title.

Kotlin vs. Java: A Few Words About Both Programming Languages

Java

Java is one of the old-school programming languages, which appeared in the late ’90s. It’s younger than dinosaurs such as C or C++; however, 25 years is a solid period, too, given that it was one of the most popular languages for many years. Designed under James Gosling’s leadership, Java is a classic representation of class-based, object-oriented programming languages. It’s a general-purpose language, even though Java is mostly associated with backend and Android development. Java code is compiled to bytecode and can be run on any platform with Java virtual machine (JVM), i.e., most modern operating systems except for iOS. For a quarter-century, Java’s arsenal includes many ready-made solutions and frameworks, both for solving backend tasks and for Android development. Java is, to date, one of the best programming languages for backend coding, and it’s unlikely that the “coffee cup” will leave the top 5 soon.

Kotlin

Kotlin is a cross-platform, statically typed, general-purpose programming language developed by JetBrains in 2011. JetBrains wanted to create a language that would compile as fast as Java and be better in everything else. Kotlin is compiled in bytecode and runs on JVM as Java. Moreover, its code is interoperated fully with Java. Developers can complete half a project with Java and the next half with Kotlin, and it will work. Frameworks developed for Java also work with Kotlin as well. The new generation language can also be compiled to JavaScript and native iOS code via Kotlin Multiplatform. 

Such languages as JavaScript, Paskal, TypeScript, HAXE, PL/SQL, F#, Go, Scala, C++, Java, C# Rust, and D influenced what Kotlin would become. The creators tried to take the best from each, and as the result and world recognition shows, they possibly achieved their ambitious goal regarding Android development.

Kotlin Vs. Java: Head to Head Comparison

You are unlikely to find a problem that you can solve with Kotlin and can’t with Java, and vice versa. They are both winners in this round of Kotlin vs. Java. Highly-skilled developers receive desirable results using either of them. Of course, this is in the context of Android and server-side development.

Despite many commonalities, these languages have many differences and thus solve the same tasks using different tools. We gathered the differences between Kotlin and Java in one place for illustrative purposes.

Kotlin vs Java: Google’s Verdict

In 2017, Kotlin officially became a programming language for Android. There was already an indication that Google saw the great potential of Kotlin—the world-known tech giant provided full support for this language even earlier, which meant they were looking for a Java substitute. The next step was Google’s announcement at the annual conference Google I/O in 2019. At this event, Kotlin was declared as the preferable language for Android development:

Today we’re announcing another big step: Android development will become increasingly Kotlin-first. Many new Jetpack APIs and features will be offered first in Kotlin. If you’re starting a new project, you should write it in Kotlin; code written in Kotlin often means much less code for you–less code to type, test, and maintain. And we’re continuing to invest in tooling, docs, training and events to make Kotlin even easier to learn and use.

Posted by Chet Haase

It’s a clear answer to the question, “Is Kotlin better than Java for Android?”, at least from Google’s point of view.

However, It’s possible that the company’s official position is not enough to convince you. Well, it might be the case. Who knows what goals Google tried to achieve by favoring Kotlin. Let’s continue our analysis on Kotlin vs. Java and look at other aspects such as performance, main features, the development community’s popularity, and use cases.

Kotlin vs Java Performance Tests

It’s always interesting to know what technology shows better performance, consumes less memory and solves tasks quicker. The table above shows the average results of the massive tests provided by enthusiastic engineer Jakub Anioła. He has done much work. All test processes are described in a series of Medium posts dedicated to comparing the performance of Kotlin vs. Java. If you are interested in which methods and tests he conducted and the results, you should read his posts.

With all due respect to this person and the work he has done, such comparison of technologies has only scientific value. It doesn’t reflect the actual performance each programming language will show when solving real-life tasks. Also, the differences between Java vs Kotlin are so minor that it’s unlikely your business software will face anything in which the differences will be meaningful. 

Returning to the main topic, Java isn’t inferior to its young opponent and even precedes Kotlin in most tests, as the table shows. This means that performance is not the reason why more and more developers prefer Kotlin over Java.

Kotlin vs. Java: Why Kotlin is Better for Android Development

The main advantage for Kotlin in the Java vs. Kotlin match is the ability to use the latest version of the programming language for Android development. 

Both languages compile their code in bytecode, which is further run in Java virtual machine (JVM). Furthermore, the version of Java has to be compatible with the JVM version. Android has integrated JVM, which is consistent with Java 7 and 8 only. This means that developers using Java for Android development can’t use Java 16 and limit themselves with programming tools released six years ago.

Kotlin doesn’t have an issue with the JVM version using an integrated compiler. Android developers can use all top-notch features of the language immediately after they are released. Given the insane speed of technology’s progression, this is the core advantage and reason why Kotlin is better than Java for the Android platform in our opinion.

Feature Which has Become a Challenge

Ironically, one of Java’s advantages became a hindrance that slowed down the development and implementation of relevant, top-line tools and features—the full backward compatibility of all versions of Java code. No doubt, this is essential functionality, but the necessity to be compatible with code that was written 25 years ago hinders Java from substituting obsolete parts with new ones and improving. This makes Kotlin code more concise and elegant compared with Java. Besides age also plays a role. JetBrains could take all Java’s weaknesses into account, creating Kotlin.

New Horizons With Kotlin Multiplatform

One more competitive edge of Kotlin regarding not only Android is support for multiplatform programming. Here, the comparison of Kotlin vs. Java doesn’t make sense. 

It’s a bit of a stretch, but Java can be called a multiplatform programming language. Still, it’s limited to a range of systems containing JVM, i.e., backend, desktop and Android applications. Kotlin, in turn, is a technology that supports true multiplatform abilities. In addition to bytecode, Kotlin’s code can be compiled in Javascript and iOS native code. 

This variability provides new opportunities for developers and makes Kotlin more attractive for business. In addition to the advantages of cross-platform development offered by React Native of Flutter, companies receive the capability to use single-business logic for desktop and web solutions. Using a single Kotlin code for various parts of the enterprise system decreases development costs and simplifies the ready solution’s support.

It’s believed that Java is a better match for enterprise system development. In our opinion, these are unsubstantiated allegations, because Java and Kotlin code is fully backward compatible and also compiled in Java bytecode.

NIX senior software engineer

Let’s look at an example:

The layer of business logic and connections with the backend have merged into one. This can reduce the amount of required code from 20% to 60%, depending on the application’s complexity and its business processes, time, and resources, accordingly. As a significant difference from other cross-platform technologies such as React Native and Flutter, each interface remains native. On one hand, this is a disadvantage, so you want to speed up the process as much as possible. On the other hand, it allows you to get a native UI, which is a considerable advantage in terms of user experience. Also, the interaction between backend and client-developers is simplified.

Kotlin Multiplatform Use Cases

Even though the Multiplatform is still in alpha version, large companies are already using it. Some companies started using it more than a year ago when Kotlin Multiplatform code was in the experimental stage. This reflects the high effectiveness of the Kotlin solutions.

We have helped many companies migrate their enterprise systems to Kotlin from Java for the last few years, and there was nobody who requested otherwise.

NIX senior software engineer

Kotlin vs. Java: Popularity and Adoption

According to Stackoverflow developer Survey 2020, Kotlin is in the top 5 most loved programming languages. Moreover, many experts who choose Kotlin are ex Java developers, and many of them claim that Kotlin code is more elegant and convenient to write.

I started my career as a Java developer. For more than ten years, I have used Java to create Android applications. Now, I, like most of the community, use Kotlin. If you give me a choice to choose a language to start a new project, it will be Kotlin, for sure.

NIX Android developer

The second chart shows the most wanted programming languages and which language responders want to utilize.

Here, the Java vs. Kotlin competition continues. Both languages are in the top 10; however, in this chart, Java lags behind Kotlin by 3.8%.

These two charts show that the development community is interested in learning and using Kotlin. You can’t buy recognition, you can only earn it.

Conclusion

In the context of Kotlin vs Java for Android, the choice is obvious, and it’s Kotlin. The younger and more modern programming language ousted Java from this area. If you need to develop a mobile app for Android, you have to look for Kotlin developers. It’s also worth remembering Kotlin Multiplatform and its impressive capabilities of using one code for different platforms.

As for backend development, Java is still in the top programming languages for this purpose. Here, it doesn’t face JVM limitations and demonstrates its full potential. Add to that ton of groundwork and tools, and one of the largest developer communities worldwide. It’s possible that in the future Kotlin will prevail on the backend side too, but for now, this isn’t the case.

If you have any questions about mobile or backend development, our experts are always ready to help.