Kotlin or Java? Which Programming language Android developer should learn?

Since Google announced @Kotlin as the official language for Android development at Google IO in 2017, programmers who want to become Android developers have been in a dilemma.

The big question in front of them is whether they should learn Kotlin or Java.

If you are a beginner who wants to learn Android development, my answer is Java. Still, if you are a Java developer who wants to jump into the lucrative market of Android app development, then my answer is Kotlin.

I’ll discuss why beginner Android programmers should start with Java and why Java developers should learn Kotlin in this article.

When I say beginners should start with Java, you may think, “What the heck? Kotlin is much more productive, has less boilerplate code, and is now the official language of Android development, and this guy is suggesting learning Java. I am not gonna fall for it….”

Well, being a Java developer, I may be a little bit biased, but I’ll try to explain the reasons why I suggest a beginner Android developer start with Java rather than Kotlin.

Beginners in Android Development Should Start With Java

The first and foremost thing is that Android development is not everything; as a programmer, you may be starting your career with Android development, but if you start with a well-established language like Java, you become a part of the bigger Java community and market, which directly means more job opportunities.

The second and more important thing is that there is a huge community of Java programmers, which means you can find answers when you are stuck.

This is very important because, as a beginner, you will face a lot of technical problems, and you might not know where to head when you are stuck.

When you search Google with a Java problem, you are bound to get answers; the same cannot be said for Kotlin, which is still a new programming language.

There are also more tutorials, books, and courses, both free and paid, which can teach you Android development with Java, like this list of Android resources for Java programmers. Still, there are few for Kotlin, especially free resources on Android development.

Things will improve over time when more and more programmers start using Kotlin, but I doubt it can ever touch the popularity and adoption of the Java programming language.

That’s why I suggest a beginner programmer who wants to become an Android developer should start with Java rather than Kotlin.

However, that’s not a hard and fast rule; if you prefer learning Kotlin rather than Java due to productivity reasons and are mostly focused on Android development, then you can sure start with Kotlin, and Kotlin Fundamentals is a good place to begin.

But, once you know Java, your journey to Kotlin will be easy and smooth because Kotlin is 100% interoperable with Java. It compiles into Java bytecode and runs on JVM.

Java Programmers Should Learn Kotlin

Now, coming back to the second set of programmers who wants to learn Android development: our fellow Java developers. For them, I think it's best to learn Kotlin because it improves productivity.

A class that takes 50 lines of code in Java can be written in just one line in Kotlin. It can help you avoid all boilerplate code like you don’t need to specify getters and setters, equals(), hashCode(), or toString() methods. Kotlin can generate all that by itself.

Here is a nice comparison between Kotlin and Java in terms of productivity and lines of code to write similar stuff:

If you don’t know, Kotlin was developed by JetBrains, the company behind one of the most popular Java IDEs, IntelliJ IDEA. They were a Java shop developing IDEs like IntelliJ IDEA, PyCharm, and ReSharper, all in Java, and built Kotlin to improve their productivity. Still, at the same time, they could not rewrite all their code in Kotlin, so they made Kotlin fully interoperable with Java.

Because Kotlin generates Java bytecode, you can use your favorite Java frameworks and libraries in Kotlin, and your Java friends can also use any Kotlin framework you develop.

Even a major Java framework like Spring has started supporting Kotlin from Spring 5. If you don’t what’s new in Spring 5, check that out.

Even though currently, almost all @android code, examples, and apps are in Java, it will change in the future because Google has declared Kotlin as the official language for Android app development.

Many companies have already started using Kotlin for their Android app development, and that’s the main reason I think Java developers should learn Kotlin.

If you decide to learn Kotlin Programming language, then Kotlin for Android: Beginner to Advanced is also a great place to begin. It’s a no-nonsense course for Java developers, which will help you to get going with Kotlin in no time.

You don’t need to start with things like what a variable and object are, as this course has the right pace and depth for Java developers compared to other beginner Kotlin courses for Android development.

If you prefer books, then Kotlin in Action is also not bad. You can learn about all the essential features of Kotlin, e.g., var vs. val, data keyword, and functional programming, by yourself.

That’s all about whether Android developers should learn Kotlin or Java. As I said, if you are a complete beginner who wants to start your career as an Android developer, you’d better start with Java.

You will not only get up to speed in no time, but you will have better community support, and knowledge of Java will help you a lot in the future. It will also help you to learn Kotlin in the future.

If you are a Java developer, you’d better start learning Kotlin to improve your productivity and also to help you become part of a lucrative niche of Java developers who know Kotlin, which may give you a competitive edge in the job market. It’s also one of the 3 JVM languages Java developers should learn on my list.

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P. S. - If you want to learn a valuable skill like Kotlin, then I highly recommend you check out these best Kotlin courses from Udemy, which are both comprehensive and very engaging. You can use this course to learn Kotlin for server-side Java and mobile app development with the Android platform.