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Kotlin and Java are two of the most widely used programming languages in modern software development. While Java has been a cornerstone of the software world for decades, Kotlin has emerged as a modern alternative, particularly in the Android ecosystem.
The choice between Kotlin and Java depends on the project needs and developer preference. Kotlin is ideal for new projects seeking efficient development, while Java suits projects needing robust stability.
This article seeks to explain the 12 main differences between both programming languages. Afterward, we'll discuss whether Kotlin is or not better than Java and highlight the main reasons.
Java is a mature, object-oriented programming language that has been around since 1995. It is an open-source, general-purpose, object-oriented programming language. It’s known for its portability ("write once, run anywhere"), extensive libraries, and widespread adoption across enterprise and Android development. In addition, since it is compiled to bytecode, it can run on any Java Virtual Machine (JVM).
Kotlin is a modern programming language developed by JetBrains, officially supported by Google for Android development since 2017. It's an open-source language that can also compile code to bytecode and run on Java Virtual Machine (JVM), enabling it to work on almost any platform. It’s designed to be concise, expressive, and interoperable with Java.
According to the Stack Overflow Developer Survey 2024, Kotlin is in the top 20 most loved languages, while Java remains among the most used.
And as mentioned, Java is a general-purpose language, and together with JavaScript and Python, it is among the most popular languages in the world. Kotlin is not yet fighting for that podium, but it has been a tough competitor when it comes to Android development.
One year after its launch, in 2017, Google recognized Kotlin as their second official language for Android development. In 2019, Kotlin was declared as the favored programming language for Android applications at Google. Consequently, it underwent incredible growth.
Now that we have a bit of context, you might wonder how Kotlin's growth impacts Java. Will Kotlin replace it? The answer is not that simple. There are a lot of mixed opinions on this subject. To understand both sides of the debates, let's first take a close look at their differences.
Kotlin’s built-in null safety features help developers avoid the infamous NullPointerException. Java now also includes better null handling through annotations and IDE tooling, but it's not as seamless or enforced as Kotlin's compiler-level approach.
Kotlin offers a more concise and expressive syntax. For example, Kotlin eliminates boilerplate getters/setters and supports type inference. Java has made improvements in recent versions, but still tends to be more verbose.
Kotlin’s type inference has improved with the K2 compiler, allowing for smarter deductions and cleaner code. Java supports limited type inference, mostly within local variables (var keyword).
Kotlin provides coroutines for asynchronous programming, which are lightweight and easy to use. Java 21 introduced Virtual Threads, providing a new way to handle concurrency more efficiently, narrowing the gap between the two languages.
Kotlin’s data classes automatically provide equals(), hashCode(), toString(), and copy(). Java's record keyword introduced in Java 16, now enhanced with record patterns in Java 21+, serves a similar purpose.
Kotlin’s compiler smartly handles type casting, and Kotlin 2.0 has made this even more efficient. Java requires explicit casting, which can lead to more verbose code.
Java forces developers to handle exceptions using try-catch blocks or by declaring them with throws. Kotlin removes checked exceptions, offering cleaner code at the cost of potentially missing error handling.
Kotlin supports extension functions, allowing developers to add functionality to existing classes without modifying them. Java doesn’t natively support this feature.
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Kotlin supports scripting and building domain-specific languages (DSLs) more effectively than Java, making it a favourite for configuration and build scripts.
Both languages are interoperable. Kotlin is fully compatible with Java and can call and be called from Java code. Interoperability is more seamless with recent improvements in both toolchains.
Kotlin continues to gain first-class support in JetBrains IntelliJ IDEA and Android Studio. Java also benefits from strong support in major IDEs and recent enhancements to debugging and profiling tools.
Java has a massive legacy ecosystem and is dominant in enterprise environments. Kotlin is growing rapidly, especially among startups and mobile developers. Both languages have strong communities and frequent updates.
Kotlin vs Java, which is better? Both have their strengths. Kotlin is more modern, with concise syntax and null safety, and is officially supported by Google for Android development. Java, however, has a larger ecosystem, mature tools and libraries. "Better" depends on your project needs.
But first and foremost, despite their differences, both Java and Kotlin compile to bytecode. Therefore, you can easily call Kotlin code to Java or the other way around, which allows both languages to be used in the same development project.
As we have explained, Kotlin does offer numerous advantages regarding Android development, but is Kotlin better than Java? Well, it does have some benefits over its competitor:
Nonetheless, let's not forget that Java also has its own benefits:
Now that we have highlighted each language's benefits, it is even harder to choose between Kotlin and Java, right? Well, let's try to take a pragmatic look.
Kotlin has been emerging as the new Android language. Its success comes from the fact that it introduces vital features that are making developers' life a lot easier, such as extension functions, lambda expressions and high-order functions, coroutines, and no NullPointerExceptions.
These are just some of the features that make it safe to affirm that, yes, Kotlin is better than Java for Android development and is likely to dominate in the future.
Is Kotlin Replacing Java? Everything seems to be moving toward Kotlin, and the new development tools that are rising know it! However, Java still has a lot of value and should not be neglected.
For general-purpose programming, Java still got it. Even for Android development, it remains an excellent language, and it is entirely understandable why some developers choose it.
Truth be told, it also depends on what languages the development team is using and which programming language feels more comfortable. These are all valid concerns. Plus, Java has been one of the most popular languages for years, so the chances of being entirely replaced soon are low.
Kotlin and Java are closer than ever in terms of capabilities, thanks to continuous improvements. If you value modern syntax, concise code, and cross-platform capabilities, Kotlin is a strong choice. For enterprise-grade scalability and long-term stability, Java remains a solid option.
Choosing between them comes down to your project requirements, team expertise, and platform goals.
Still not sure which language is right for your next project? Get in touch with our expert development team. We’ll help you evaluate your needs, build a tailored tech stack, and bring your ideas to life with the right tools from day one.
It depends on your goals. Kotlin is modern, concise, and well-suited for Android apps. Java is stable, widely used in enterprise environments, and has a massive ecosystem.
Kotlin didn't fully replace Java, but it became Google's preferred language for Android due to its safer syntax, conciseness, and modern features like coroutines and null safety.
Yes, Kotlin can do everything Java does. It runs on the JVM, is fully interoperable, and can use all Java libraries and frameworks.
Kotlin has a steeper learning curve for some developers, slower compilation in certain contexts, and a smaller community compared to Java.
If you're focused on Android development, start with Kotlin. For broader backend or enterprise work, Java may be a better foundation.
Yes! Kotlin is 100% interoperable with Java.
Marketing intern with a particular interest in technology and research. In my free time, I play volleyball and spoil my dog as much as possible.
Software developer with a big curiosity about technology and how it impacts our life. Love for sports, music, and learning!
CEO @ Imaginary Cloud and co-author of the Product Design Process book. I enjoy food, wine, and Krav Maga (not necessarily in this order).
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