Programming Languages

What Is Kotlin? Inside the Android Programming Language

Written By April Bohnert | November 15, 2023

Abstract, futuristic image generated by AI

In 2010, developer tool vendor JetBrains set out to address some of the common challenges and pitfalls faced by developers using Java and other programming languages. They wanted to design a language that was more expressive, concise, and safer, ultimately improving developer productivity and satisfaction. The result was Kotlin, a modern programming language that has transformed the way developers approach coding. 

In this article, we’ll take a closer look at what makes Kotlin stand out, its key features and advantages, its use cases, and the skills tech teams need to get the most out of this versatile language. Whether you’re a hiring manager, tech recruiter, or a tech professional, this article will provide you with valuable insights into the world of Kotlin.

What Is Kotlin?

Released in July 2011 under the name Project Kotlin, Kotlin is a statically typed programming language that runs on the Java Virtual Machine (JVM) and is designed to be fully interoperable with Java. This means developers can use the vast ecosystem and libraries of Java while also taking advantage of Kotlin’s more modern features and syntax. Kotlin also eliminates much of the boilerplate code required in Java, making it easier to write clean, reliable code. 

Kotlin’s most notable impact, however, has been in the realm of Android development, where Java was the go-to language for years. Google announced official support for Kotlin on the Android platform in 2017 and has since been moving more and more toward a “Kotlin-first” approach to Android development. Today, over 60% of Android developers have adopted Kotlin as their language of choice, and it is used in 95% of the top 1,000 Android apps

But Kotlin’s capabilities extend beyond just Android development. Its concise syntax, powerful features, and interoperability with Java make it an excellent option for a wide range of applications ranging from server-side development to web development.

Key Features of Kotlin

Kotlin brings together the robustness and universality of Java with the modern touch and simplicity that today’s developers crave.


Kotlin is designed to be more concise than Java, which means developers can write less code to achieve the same functionality. This is possible due to Kotlin’s support for type inference, which allows the compiler to infer the data type of a variable or expression based on its context. This eliminates the need to explicitly declare the data type in many cases, reducing boilerplate code. For example, in Java, you might write: List<String> myList = new ArrayList<String>();

In Kotlin, you can simply write: val myList = ArrayList<String>()


Kotlin is designed with safety in mind and includes several features that help prevent common programming errors. For example, Kotlin’s type system is designed to eliminate the dreaded null pointer exception, which is a common source of runtime errors in Java. In Kotlin, all variables are non-nullable by default, and you must explicitly declare a variable as nullable if you want it to be able to hold a null value. This makes it much easier to write safe, reliable code.


One of Kotlin’s biggest strengths is its interoperability with Java. Kotlin code can be easily mixed with Java code in the same project, and you can call Kotlin code from Java and vice versa. This makes it easy to gradually adopt Kotlin in an existing Java project, or to use Java libraries in a Kotlin project. For example, you can use the following Kotlin code to call a Java method: val result = MyJavaClass().myJavaMethod()


Kotlin is well-supported in a range of development tools and integrated development environments (IDEs). For example, Kotlin is fully supported in Android Studio, which is the official IDE for Android development. This means that you can take advantage of all the powerful features and tools in Android Studio when developing Kotlin code. Additionally, Kotlin has excellent support in other popular IDEs like IntelliJ IDEA and Eclipse.

In the next section, we’ll take a closer look at some of the advantages of Kotlin over other programming languages.

Advantages of Kotlin

Faster Development

Thanks to its conciseness, simplicity, and powerful tools, Kotlin can significantly speed up the development process. Developers can write less code and achieve more functionality, reducing the time and effort required to build software. This is especially beneficial in the fast-paced tech industry, where time to market can be a critical factor in the success of a project.

Improved Code Quality

Kotlin’s safety features and modern syntax contribute to better code quality. By reducing the likelihood of common programming errors such as null pointer exceptions, Kotlin helps to make software more reliable and robust. Moreover, the modern, expressive syntax of Kotlin makes code easier to read and maintain, further improving the quality of the software.

Developer Satisfaction

Kotlin’s modern syntax, powerful features, and tool support contribute to a more enjoyable development experience. Developers can focus more on solving problems and building great software, and less on dealing with boilerplate code and common programming errors. This leads to higher developer satisfaction, which can translate into higher productivity and better-quality software.

Explore verified tech roles & skills.

The definitive directory of tech roles, backed by machine learning and skills intelligence.

Explore all roles

Use Cases for Kotlin

The versatility of Kotlin makes it an excellent choice for a variety of projects, from mobile and server-side development to web development and beyond. Let’s delve into some of the key use cases for Kotlin.

Android Development

Kotlin has become the go-to language for Android app development since Google announced official support for Kotlin on the Android platform in 2017. The language’s features make it an ideal choice for building high-quality Android apps. Many of the top apps on the Google Play Store, including Airbnb, Netflix, and Uber, have been built with Kotlin.

Server-Side Development

Kotlin is also a popular choice for server-side development. It can be used with a variety of server-side frameworks, such as Ktor, to build scalable and performant web applications and APIs. Kotlin’s interoperability with Java means that you can take advantage of the vast ecosystem of Java libraries and frameworks when building server-side applications.

Web Development

Kotlin is not only great for Android and server-side development, but it also shines in web development. With Kotlin/JS, you can compile Kotlin code to JavaScript for front-end development. And for the back end, frameworks like Spring Boot have got you covered.

What’s exciting is the recent advancements in WebAssembly (Wasm) that have opened new doors for Kotlin in web development. JetBrains and Google now provide experimental support for Kotlin on WebAssembly, enabling faster performance and effective code sharing between Android and web platforms. Early experiments show Kotlin code running up to 2x faster on WebAssembly compared to JavaScript. This is indeed a game-changer for Kotlin developers venturing into web development.

Other Use Cases

Kotlin is a versatile language that can be used for a wide range of other applications, from data analysis and machine learning to game development and more. Its powerful features and modern syntax make it an excellent choice for any project where you would traditionally use Java.

Key Kotlin Skills

Developing with Kotlin requires a mix of technical and soft skills to truly leverage the language’s capabilities. Key skills Kotlin developers need include:

  • Understanding of Kotlin Syntax and Concepts: This includes understanding how to work with data types, control flow, functions, and classes in Kotlin. A thorough knowledge of Kotlin’s syntax will enable developers to write clean, efficient, and effective code.
  • Experience with Java and the JVM: Since Kotlin is interoperable with Java and runs on the Java Virtual Machine (JVM), experience with Java is highly beneficial. Understanding how Java and the JVM work will help developers write better Kotlin code and leverage the vast ecosystem of Java libraries and frameworks.
  • Familiarity with Android Development: For those looking to use Kotlin for Android apps, familiarity with Android development concepts and tools is essential. This includes understanding how to work with the Android SDK, Android Studio, and related tools and libraries.
  • Problem-solving Skills: Problem-solving is a crucial skill for any developer, and Kotlin developers are no exception. Developers should be able to think critically and solve complex problems efficiently.
  • Communication and Collaboration: Finally, strong communication and collaboration skills are essential. Developers should be able to work effectively in a team, communicate ideas clearly, and collaborate with other team members to achieve common goals.

Harnessing the Power of Kotlin

It’s clear that Kotlin is on a trajectory to become even more integral in software development. With more developers and companies adopting Kotlin, the ecosystem around this powerful language continues to evolve and expand, opening up new possibilities and opportunities. By understanding how Kotlin works and the skills needed to leverage it, you’ll be well prepared to tap into the potential of this versatile language and set your projects up for success.

This article was written with the help of AI. Can you tell which parts?

Abstract, futuristic image generated by AI

7 Android Interview Questions Every Developer Should Know