Kotlin vs. Java: Which Is Best for Android Development?

As a developer, finding the right tech stack matters when so many new languages seem to be popping up everywhere. It’s important to compare and find the right one for your project.

Android apps dominate the global market, and consequently this has increased demand for Android developers. Businesses have recently been forced to go remote, which has accelerated the demand for more talented developers.

There has never been a better time to be a developer. And it's essential that you, as a developer, have the right programming language as part of your skillset. In today’s article, we’ll take a look at the two top contenders for the best programming language for developing Android apps.

We'll compare Kotlin and Java in five different categories to see which is the best. Java has been the favored programming language for Android apps for a long time. When Kotlin first came into the picture, I gave it little thought and assumed it was just another passing fad. Once I started learning and using Kotlin, it quickly became clear why the community had taken to it.

What Is Java?

Java is a powerful open-source, multi-platform, object-oriented language. Its creators designed it with fewer implementation dependencies. Being compiled on bytecode means that Java can run on any Java Virtual Machine (JVM). It does very well on large resource-hungry apps. Java also has a wide variety of well-developed, powerful tools such as Eclipse, NetBeans, IntelliJ IDEA, etc.

What Is Kotlin?

By comparison, Kotlin is a fairly young language. Inspired by Java, Kotlin was designed to be faster, cleaner, and more concise. It's the brainchild of JetBrains, the developers of Android studio. The language provides a mix of object-oriented and functional programming. Kotlin is designed to run on a JVM, so it can run alongside Java. It has gained popularity in the Android developer community. In May 2019, Google announced that Kotlin is the preferred language for Android apps in the Google Play store.

Java vs Kotlin

1. Ease of Learning

Java is more complex but easier to learn. Kotlin is clearer, but mastering it is harder.

Java is a heavily typed language that has strong syntax rules. Its verbosity is what makes it a great option for beginners. Java forces programmers to type out what they mean instead of adding syntax sugar. This verbosity is also a Java weakness, which we’ll tackle in a later category.

Kotlin, on the other hand, is more concise, which makes for fewer lines of code, subsequently requiring a steeper learning curve for beginners. For experienced programmers, learning Kotlin will be a breeze. They will be better able to appreciate all the benefits that Kotlin offers. Java provides more learning material, but both languages include excellent documentation. Most beginner tutorials will be written in Java. Having a more active community than Kotlin, Java clearly wins this round.

Winner: Java

2. Which Language Has a Bigger Community?

Java has been around for well over two decades, so it definitely has that advantage over Kotlin. You should have no trouble finding a large community of developers who have been working in that space for a long time. Finding answers to most of your questions is going to be easier than if you have trouble with Kotlin. Java can be a bit tricky for people coming from languages like JavaScript due to it being heavily typed and its strict syntax rules.

There are plenty of articles, blogs, and YouTube videos readily available to help you with Java. Kotlin, on the other hand, is relatively new, so although its community is getting stronger by the day, unfortunately it isn't as mature as Java's. Finding answers to questions can sometimes be difficult, and finding experienced mentors is even harder. Java is the clear winner here due to its robust and rich community.

Winner: Java

Source: Google Trends

3. Maintainability

Kotlin clearly has the advantage in this category. Concise, clear, and fast, Kotlin includes about 20 percent less boilerplate code than Java. This means you’ll be solving complex problems using less code. Less code is always good because it decreases the chances of bugs in your code. Due to Java's verbosity, you’re going to write more lines of code, which means there will be more room for those pesky little bugs to creep in. It’s also a lot harder to maintain bloated code, and adding or removing something can cause your code to crash. Kotlin is typically easier to maintain since it’s less verbose. By writing less code and writing fewer tests for the code, we decrease the chances of bugs and app crashes.

Winner: Kotlin

4. Syntax

One of the first lines of code developers will write is a Hello World program. Java and Kotlin are both heavily typed languages. As pointed out earlier, Java has strict syntax requirements and is a verbose language. Java's verbosity requires the programmer to explicitly write what they mean. This results in more lines of code. Meanwhile, Kotlin is a concise language that requires fewer lines of code to achieve the same result. Concise code has advantages like maintainability, readability, and faster execution, making it easier for other developers to read and understand your code. Kotlin's conciseness makes it the winner of this category.

Winner: Kotlin

Example: It’s clear that writing something as simple as Hello World requires more lines in Java than it does in Kotlin.

5.Which Language Is More Testable?

Testing is an important part of developing real-world applications. The last thing you want is to publish an app that crashes or doesn’t perform how a user expects it to function. There are three common tests that all Android developers should be aware of and know how to test for: UI, unit, and integration tests.

Writing tests will definitely prove easier for Java than for Kotlin simply because of the rich content that is out there that teaches people how to test all the different components that make up an Android app. The tests themselves will look pretty similar, plus you could always use a tool like Waldo, a no-code testing solution that takes out all the nitty gritty of testing. Even nontechnical members of your team can use Waldo without a steep learning curve. Due to its readily available resources on how to test more complex Android-specific components, Java is the winner in this category.

Winner: Java

Example: There isn't a noticeable difference in difficulty when writing tests for these two languages.

Wrapping It All up

With of a score of three out of five, Java is the clear winner. Its popularity, readily available resources, and ease of learning makes it the top choice for building Android apps. Easily accessible to developers at all skill levels, Java also has an active, millions-strong community. Kotlin was a strong contender with its concise and clear code. However, it just cannot compare with Java’s decades of experience. Kotlin at present is better suited for smaller apps as well as microservices. You can still incorporate Kotlin into your project, but Java will probably work better as the main language. Java isn’t going anywhere anytime soon as it’s still very much in demand. Learning Kotlin would be advisable, but right now Java is still the best option for Android apps.

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This post was written by Sinazo Bogicevic. Sinazo is a software developer with a passion for blockchain and mobile development. When she's not creating amazing products, she can be found either writing or talking about tech for the not so tech-savvy.