Kotlin vs. Java: Which Is Best for Developing Android Apps?

May 09, 2022
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In July 2011, JetBrains, a software development firm formerly IntelliJ Software, unveiled Project Kotlin, a modern, all-purpose and intuitive programming language. With the 10th Anniversary this year, the Kotlin going forward even stronger making it one of the preferred languages for modern app development with a solid footprint in the Android world.

If we talk about numbers, 4,800,000+ people used Kotlin over the last 12 months for server-side, mobile multiplatform, Android, and front-end development. To date, its statistics look interesting. There are 194+ Kotlin User Groups around the world with 45 of the top 200 universities teaching Kotlin, its adaption by top software companies like Twitter, Netflix, Airbnb, Pinterest, Uber, Careem, Philips, Stanford University and Amazon are some of the few. Its rapid growth clearly depicts that it would be marked as the top language for years to come.  As a matter of fact, Google recognized Kotlin and made it the second official language for Android app development.

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Why Kotlin?

Kotlin is a modern-day but already mature, concise and safe programming language, which is easy to pick up. We can create powerful applications in no time. The thing which makes it powerful is its ability to be multi-platform targeted. Along with this one of the biggest advantages is that it reduces time spent writing and maintaining the same code, business logic and connectivity for different platforms like Android and iOS while retaining the flexibility and benefits of native programming. The code-sharing also bring benefits in connected application where the logic can be used again on both the server and the client-side running in the browser.

Kotlin: Now?

Kotlin now stands at version 1.6 which is the latest release of 2021. This release delivers stable language features such as JVM records which is a new way to declare a type in the Kotlin language. Another improvement is in sealed interfaces that infers restricted class hierarchies providing more control over inheritance. Another improvement is in inline classes and includes the new default JVM IR compiler which is an internal representation used by the Kotlin compiler when it parses Kotlin source files. Other highlighting features are suspending functions as supertypes, better support for recursive generics, various additions for annotations, and Java interoperability. Other than these programming features, Kotlin now has its own YouTube channel, a new logo and has been embraced by top software companies.

Where is Java?

Java is an old contender and has been around since 1995, developed by James Gosling at Sun Microsystems (which in 2009 acquired by Oracle) that is still in high demand. Java developers are being most searched by talent hunters around the globe due to the vast implementation of software in Java to date. Having its strong basis in object-oriented programming and being the top 10 programming languages in successive years, Java is not going anywhere. The matter of fact is that most of the Java developers would adopt Kotlin being the closest programming language. Java developers already have a good level of understanding of OOP concepts that would easily transition them to a newer language. This transition is natural. As we know that no programming language is perfect and even Java is no excuse. The complications in Java can make a developer’s job tiresome and repetitive. Kotlin will provide solutions to common programming annoyances and improve the Java ecology.

Java vs Kotlin

As mentioned earlier, Kotlin is a modern programming language that has tackled the issues which were faced by earlier languages like Java, it is being loved by the developers’ community due to its brevity, conciseness and cleaner syntax as well as light-weightiness. Kotlin is clearly designed to improve existing Java models by providing solutions to API design inefficiencies.


Kotlin deals with a number of Java’s shortcomings:

Null Safety

In the developer’s world, null pointer exceptions are famous and are the cause of most of the headaches. In Kotlin it is not possible to assign null values to variables or objects by default. If we try to run the code it will fail at compile time. Hence, there are no NullPointerExceptions. With this handling enabled, Kotlin is in a superior league from other languages.

Less Code

The biggest gain a developer can get from any programming language is of writing less code. Ironically this is one of the key differences between Kotlin and Java. Kotlin requires much lesser code since it is very concise. This also reduces the chances of making code errors by the developers.

Data Classes

In Java, developers need to create the fields (or variables) to store the data, the constructor, and the getter and setter functions for the fields/variables. We know that these classes are mainly intended to store data and have zero (or very little, at most) functionality. To solve this, Kotlin provides a more straightforward way to create classes to hold data by simply including the “data” keyword in the class definition. With this definition, the compiler will easily auto-generate the constructor and the getter and setter functions for several fields/variables.

Lambda Expressions

Lambda expressions that are synonymous with anonymous functions (considered as “functional literals”) are put to best use in Kotlin. To elaborate further, lambda expressions represent a function that is not declared and immediately passes as an expression. In contrast to this, Java is limited to the concept of pure object-oriented programming. Although it has been taking some steps toward functional programming too, in comparison to Kotlin it doesn’t suffice. Like back in 2014, Java version 8 introduced lambda expressions with a little difference which is that lambda expressions in Java can be passed as objects and can be executed on demand.

Kotlin vs Java performance

For any android developer the compile-time matters. When you’re creating and debugging your Android applications you will likely have to compile and recompile countless times. Having a quick compile-time does marvels for development teams.

See Also: Flutter or Java? Where Are Android Developers Going?

In the battle between Kotlin vs Java performance, Java does beat Kotlin by 10–15% for clean builds. But in the practical world a much-desired functionality required by most developers is partial builds, where incremental compilation makes large improvements. Since Gradle is the default for Kotlin, and with its daemon running and incremental compilation turned on, the clash between Kotlin vs Java performance, Kotlin compiles as fast or slightly faster than Java.


In the debate between Java vs Kotlin, and specifically for developing Android apps, Kotlin seems to be a clear winner. Since Kotlin is an official language and a professional language for Android app development as announced by Google, so it is the right choice to select Kotlin vs Java. Good documentation of a programming language is always welcomed by the developer’s community. For this, it has a structured document for each, and every task and one can easily get a reference from it. Finally, one strong reason for investing your time in Kotlin is that it is an open-sourced language and there is no requirement to spend money on costly licenses.

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I am a senior technical project manager in a reputable US based software development company. I have been developing and managing innovative solutions for multinational companies, deployed software and systems. I am responsible for full life cycle development of next-generation software, from initial requirement gathering to design, coding, testing, documentation and implementation. Being in technology I love to write about it.

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