What Are the Biggest Advantages of Kotlin over Java? 8 Reasons to Try It for Android Development 

Is it about time that your reconsidered Java as the go-to language for your Android-based projects? And to switch over to Kotlin, the (not so) new support language for Android development, maybe? But what's behind its surging in popularity among developers? In other words: what are the biggest advantages of Kotlin over Java?

Why should you even consider trying it as an alternative to sometimes problematic, yet familiar and reliable Java? Now here are some of the best answers to your legitimate question:


But First: What's the “Problem” with Java? 

“Its age” I should say.

Just think about it:

Java was released 20 years ago. Therefore, it has been piling up a legacy baggage that's now dragging it down — each new version of Java has to be compatible with the previous one.

In short: competing with newer, lighter, more concise, more expressive and state-of-art feature-packed programming languages turns into an unfair challenge for Java.

Now don't think that Kotlin's already eclipsed it! Not even close:

Java's still the official programming language for Android development.

Yet, it does start to show its limitations. And the well-known issues, that it's challenging developers with, have started to grow from “all too familiar” problems to some major sources of frustration.

Its younger rival here has 2 key advantages in this Kotlin vs Java “competition” for winning over developers:

  • it leverages precisely the language design expertise built up over these last 20 years since Java's been around
  • it's been packed with all the much-needed modern features that Java mobile developers have been longing for; programming language features that have already proven their efficiency with large-scale projects


Introducing Kotlin: The Newer Language Running on Java Virtual Machine 

Now if Java's been the go-to programming language for all Android matters, Kotlin here is the “one-stop language” for all application development. 

Being entirely interoperable with Java — you get to use Kotlin code from Java and the other way around  — and easy to compile to Native or JavaScript for developing code that can run on iOS, as well, Kotlin's versatility is just... mind-blowing.

And here's how Andrey Breslav', Kotlin project's lead, motivates JetBrain's decision to develop this open source, statically typed, (JVM-based) language in the first place:

“We have a huge Java codebase developed over a decade, IntelliJ IDEA, and we wanted to switch to a better language without abandoning the code we already have”.

Some of the main goals of the Kotlin's development team for their new language, goals that rapidly turned into the biggest advantages of Kotlin over Java were:

  • efficient, familiar development tooling meant to boost developers' productivity
  • a good compiler 
  • seamless integration with the existing infrastructure (Kotlin's compatible with all Java frameworks and libraries and it's designed to integrate easily with Marven and Gradle build systems, as well)
  • enhanced run-time performance 

Summing up: since it's completely interoperable with Java, designed to run on the Java Virtual Machine, you can use Kotlin anywhere that you'd normally use Java. 

And this “bi-directional use” of Kotlin will only enable you to:

  1. tap into the massive Java codebase built up over these last 20 years
  2. leverage its modern features designed to streamline mobile development


The 8 Biggest Advantages of Kotlin over Java 

And now let's get straight to answering the question that's been “bugging” you:

Why would you even consider trying Kotlin in your future mobile app projects?

Here are the 8 strongest reasons why, as an Android developer, you should start seeing this programming language as a viable alternative to good old Java:


1. It's Completely Interoperable with Java 

As already mentioned here, one of the biggest conveniences with using Kotlin is that:

It's entirely compatible with Java!

… with all its tools and frameworks, that you can just add to your Kotlin projects, nice and easy, with no need to change the entire project in Java.

Therefore, it goes without saying that, once/if you make up your mind to switch over to Kotlin, migrating your project from Java is... piece of cake.


2. It's (way) More Concise than Java 

And this is, undoubtedly, one of the biggest advantages of Kotlin over Java Android:

Being able to solve the same problems using fewer lines of code can only translate into a more reliable code and fewer bugs and crashes on the UX side.

Not to mention all the other benefits that derive from code conciseness:

  • your code becomes easier to maintain 
  • … easier to read
  • … easier to apply changes to when needed

Some of Kotlin's features “responsible” for its code conciseness are:

  • data classes
  • smart casts
  • type interface
  • properties


3. Its Code's Safer 

We've already settled that Kotlin's code is way more concise, therefore it goes without saying that:

A concise, compact and clear code is implicitly a safer code!

Being more compact, it allows fewer errors. And I should mention here that it's by design that Kotlin prevents common programming mistakes, translating into:

  • fewer crashes
  • a reduced no. of system failures 

“But what do you mean precisely by “preventing mistakes from design"?” you might ask yourself.

I mean that developers get encouraged to consider the potential issues that their code might present from an early stage of the app's development process. And thus, to be cautious and to write more robust and stable code in production.


4. It Comes with a Smarter and Safer Compiler 

Adding a good compiler has been one of Kotlin's development team main goals when they created this programming language.

Therefore, its compiler:

  • detects errors at compile time, not at runtime, leveraging the “fail-fast” principle
  • performs lots of checks, thus reducing runtime errors and the no. of bugs in the code 


5. It's Easier to Maintain 

It's not for no reason that Kotlin's a “one-stop language” for all application development:

It supports lots of IDEs, Android Studio here included.

Therefore, you're free to use all those already tried and tested development tools that you're comfortable with for maintaining your codebase at scale. Another one of those "hard-to-resist-to" advantages of Kotlin over Java.


6. It's Been Created to Boost Your Productivity

Another one of the key advantages of Kotlin over Java is that:

It has been built with developer productivity in mind.

And it goes without saying that enhanced productivity goes back to its concise code itself, to its intuitive syntax and its overall clean language design:

It'll take you less time to write new code in Kotlin, to deploy it and to maintain it at scale.

And there's more to boosting developer productivity in Kotlin than “just” its concise and clear code.

In this respect, this language's been “equipped” with lots of powerful features that speed up every-day development tasks:

  • object declarations
  • parameter values
  • extension functions


7. It “Spoils” You with Better Support for Functional Programming 

What does this mean?

It means that:

  • you can improve your mobile apps' performance via inlining 
  • you can “joggle with” functional concepts in a more explicit and concise way
  • … since in Kotlin you have proper function types at hand to use in this respect


8. It Has Null in Its Type System 

And nullability issues have been one of Java's well-known sore points.

Since it's a common thing in Android for the absence of certain values to be represented as “null”, Kotlin comes to address these issues by placing null right in its type system.


Final Word 

One thing's for sure. Or two things, actually:

  1. Java isn't going anywhere and it will be long till it gets completely phased out by shiny and new Kotlin 
  2. Kotlin, on the other hand, is here to stay, to get even more developer-friendly and to win over more and more big names — I'm thinking here of Atlassian, Pinterest, Basecamp, Coursera, who've all leveraged Kotlin's new features in their mobile apps  

Therefore, who am I to tell you that you should migrate from Java to Kotlin? I can only but advise you to... take it for a spin.