Kotlin vs Java Battle: Which One Is Better?

How did Kotlin replace Java?

Kotlin vs Java battle is like a boxing match between a world champion and a younger player trying to take the title.

Kotlin first appeared in 2011, and since then, it has slowly replaced the Java language. Today, it is one of the most modern languages and official programming languages for Android.

What are the main differences between Kotlin and Java, which one is better, and why did Java lose 1st place? In this article, we will discuss some of the most important features of Kotlin and Java to help you decide which one to use.

What is Kotlin?

Kotlin is a statically typed, concise, interoperable, and safe programming language for developing Android apps. It runs on a JVM (Java virtual machine) and can be compiled into JavaScript code or used in the LLVM compiler.

The language was developed by the JetBrains company and is named after the Kotlin island near St. Petersburg.

Although its syntax is not compatible with Java, Kotlin is designed for full interoperability with Java code. Kotlin has fewer lines of code, and significantly reduces boilerplate code, which helps developers in writing clean, concise, and better code.

It is a concise, secure, and pragmatic language created to overcome the shortcomings of Java, such as null pointer exceptions (causing app crashes), no more raw types, proper function types, etc.

Kotlin became the recommended language by Google, and today it is the leading programming language in developing Android applications.

What is Java?

Java is an open-source, general-purpose, and object-oriented language developed by James Gosling in 1995.

It used to be the primary choice for most developers because Android itself is written in Java.

Java backend technology can be used for both website development and (Android) mobile application development.

Why Kotlin became the 1st choice for native Android development?

Kotlin and Java are both free and open-source, statically typed, functional and object-oriented languages. But let’s see the differences between these two programming languages, their key features, and advantages.

Kotlin features

Uses extension functions

We can extend a class with additional functionalities without changing the existing code.

Compatible with Java

It is possible to create “mixed” projects containing files written both in Java and in Kotlin.


Kotlin is efficient, easy to understand and learn, and quite effective in coding your applications.

Excellent support of development environments from day one

Support within development environments has enabled faster language learning, making fewer mistakes, and writing better quality code.

Companies using Kotlin: Google, Amazon, Pinterest, Coursera, Trello, Foursquare.

The only things Java has and Kotlin doesn’t:

  • Checked exceptions
  • Primitive types that are not classes. The byte-code uses primitives where possible, but they are not explicitly available.
  • Static members are replaced with companion objects, top-level functions, extension functions, or @JvmStatic.
  • Wildcard-types are replaced with declaration-site variance and type projections.
  • Ternary-operator a ? b : c is replaced with if expression.

Java features

Platform Independent

When Java is compiled, it is compiled into platform-independent bytecode distributed over the web and interpreted by the JVM (Virtual Machine) on whichever platform it runs.


Java’s compiler generates an architecture-neutral object file format and makes the compiled code executable on many processors with a Java runtime system.


Because of being architecture-neutral and having no implementation-dependent aspects of the specification, Java is portable.


Java eliminates error-prone situations by emphasizing compile-time error checking and runtime checking.


Java is more dynamic than C or C++. Java programs carry a large amount of runtime information that can be used to verify and resolve accesses to objects at runtime.

Companies using Java: Netflix, eBay, Uber, Apple TV, Airbnb, Pinterest, LinkedIn.

What are the limitations of Java?

Nullability Problems

The biggest frustration for Java developers that use non-nullable variables is NullPointersExceptions. Null is usually used to denote the absence of value, so Java developers have to write a few additional lines of code to find a way around this issue.


Java requires much more coding than Kotlin and most of the other programming languages. Because of Java verbosity, there are many risks of bugs and errors.

Kotlin vs Java: Which one to choose when building an Android app?

How good is Kotlin? Well, it is currently the best option for Android development. Nowadays, almost every company uses Kotlin to build native Android apps. If you are thinking about a future project, you should focus on development under Kotlin because it has many advantages.

In Async Labs, we understand both programming languages in depth. Kotlin is the clear winner in almost all aspects of Java and remains a preferred programming language.

Despite Kotlin’s advantages, Java remains an excellent general-purpose language and still has its place in the market. However, when it comes to mobile development, Kotlin is definitely the preferred programming language.

Find this article helpful, but want to know more? For more info, read our full article about Java and Kotlin.

Have other questions regarding Android app development? Feel free to write to us at hello@asynclabs.co!




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