Recalling the times, when java originated and is widely used for Mobile App Development. From almost two decades, Java was the prime programming language to build Android Apps, also ruling the Android world until the introduction of Kotlin. At Google IO 2017, Kotlin announced as the official programming language for Android app development. Since then, Kotlin vs Java has become a raging debate.

With 67%, Java is the 2018s’ second most popular language on GitHub after JS (with 97%). Whenever anyone thinks about an Android App Development, Java is the first language that springs up in mind. However, Kotlin (which is relatively new and launched by JetBrains) is challenging the Java’s popularity in the Android App Development community. Kotlin is fully supported by Google, and it is directly added in the IDEs’ installation package itself, as an alternative to the Java compiler. One who knows Java for Android Development can easily jump into a pool of Kotlin.


Kotlin is a statically-typed, and an open-source programming language that runs effectively on the Java Virtual Machine, developed by JetBrains. But it can also be compiled to JavaScript or Native to build code that can run on iOS. In the recent survey by Jexenter, Kotlin ranked 6th as the Top Technology Trends. Business leaders (Such as Atlassian, Pivotal, Evernote, Pinterest and Uber) are using Kotlin for Android app development, as it is fully compatible with existing Java stacks using just a Plugin. One can easily switch from Java to Kotlin. The pros of Kotlin:

  • To help app developers build clean APIs, Kotlin has smart extensions
  • Kotlin has null in its type system; solving nullability problems of Java
  • Kotlin is more concise, requires less code and hence there are fewer options for errors
  • Kotlin is interoperable with Java

Both are popular powerful enough and in the Android App Development Community, however, Some Java issues addressed in Kotlin:

  • The Null references are being controlled by the type system.
  • Kotlin is not having checked exceptions
  • Arrays in Kotlin are invariant
  • Kotlin is not having any raw type
  • Kotlin has proper function types, as opposed to Java’ SAM-Conversions
  • Kotlin has an excellent IDE Support. The Android Studio offering extensive IDE support to Kotlin. The integration with IntelliJ IDEA (Jetbrain’s own platform) framework offers a significant range of productivity tools. Moreover, one can configure the Kotlin Plugin within minutes within the Android Studio. The add-on support of IDE makes coding in Kotlin, debugging, unit testing and navigation easier for developers.
  • Kotlin is more versatile than Java as it is designed in such a way that experts believe that it did very well addressing some of the issues in Java. The inbuilt null checking feature of Kotlin helps avoid frequent errors.


Read More: Introduction to Kotlin for Android App Development Services


Kotlin vs Java

Now, the question is jumping from Java to Kotlin will be fruitful or not? Well, it depends on preferences. A comparative study of both the languages as described below will help you differentiate between Java and Kotlin.

Extension Functions

In Java, the extension functions are not available. To extend the functionality of the present class, developers need to create a new class and then inherit the parent class. In Kotlin, App Creator can easily extend the existing class with all new functionality. To extend, developers are able to create extend functionalities by prefixing the name of a class to the name of a specific new function.

Checked Exceptions

In Java, developers are able to declare and catch the exception as it has checked exception support. That’s why Java has robust code with a good error handling capabilities. However, Kotlin does not have any checked exceptions, so developers do not need to catch or declare the exceptions.

Null Safe

In Java, NullPointerException is a real pain for app developers. Developers are able to assign null to any variable. However, while fetching an object reference which has a null value, it raises a null pointer exception that the developers needed to handle. Kotlin tried to fix the same issue by making all types of variables non-null by default. Which means developers cannot assign null values to any variable. When the App Developer assigns null values, Kotlin code will fail while compile-time. However, one can declare a null value.

Data classes

In Java, to have the class that hold data but nothing else, the developers need to define constructors, variables to save data, setter and getter methods. However, in Kotlin to have a class that save data, developers can declare a class with the keyword ‘data’ in the class definition. Afterwards, the compiler will finish the job such as creating constructors, getter and setter methods for numerous fields.

Functional Programming

Until Java 8, it was not having any functional programming support. It supports the only subset of Java 8 features while the mobile app development. Kotlin is both the procedural and functional programming language, consists of a number of methods for developers including operator overloading, lazy evaluation, lambda, higher-order functions, etc.

Implicit Widening Conversions

In Kotlin, there is no support implicit widening conversions for numbers, hence smaller types are not able to get converted into bigger types. However, Java supports implicit conversions and in Kotlin if you want to assign the value of type Byte to an Int variable, then you need to perform an explicit conversion.

Inline Functions

Closures are the variables which cannot be accessible in the body of the function. Making the use of higher-order functions can impose a number of runtime penalties. Each function in Kotlin is an object, also it captures a closure. Both function and classes call for memory allocations, along with virtual calls introduce runtime overhead. Such overheads can be avoided by inlining the lambda exceptions in Kotlin. For example the lock() function. Java does not provide support for inline functions. However, the Java Compiler is capable of performing inline using the final method, because the final methods cannot be overwritten by sub-classes. Also, a call to the final method is resolved at a compile time.

Native Support for Delegation

In the programming technology, delegation means the process where a receiving object delegates operations to the second delegate object. Kotlin provides support for composition over inheritance design pattern, by means of a first-class delegation. Which is also known as implicit delegation. Class delegation is the alternative to the inheritance in Kotlin. This makes it possible to utilize multiple inheritances. Moreover, Kotlin’s delegated properties prevent the duplication of the code.

Primitive Types

There are in total 8 primitive data types, including char, float, double and int. In Java, variables of the primitive type aren’t objects. It means they are not the objects instantiated from the class or struct.

Smart Casts

Kotlin comes with the smart casts feature to automatically handle such redundant casts. There is no need to cast inside a statement provided, in kotlin, it is already checked with ‘is operator’ in Kotlin. Wildcard Types In a generic code the ‘?’ represents an unknown type, and known as the wildcard. There are a number of uses of a wildcard, including as local variable, type of a field, or a parameter. Java offers this wildcard types, Kotlin doesn’t. In Kotlin, it has two different ways; declaration-site variance and type projections, both as an alternative to wildcard type.

So what will it be? Kotlin or Java.

Kotlin is an enhancement to Java, not a replacement. Obviously, some features are better in Kotlin, while for other functionalities Java is advantageous to use. Also, there is another way around for those, who do not want to ditch any of these two leading programming languages. Both Java and Kotlin - programming languages are fully interoperable as well as compile to bytecode. It means it is now possible to call Kotlin code from Java and vice-versa. There are two advantages of this flexibility, the foremost one is, and it facilitates getting started with Kotlin by introducing the Kotlin code in Java project. And the other is, both languages can be used simultaneously in any Android App Development project.

Read More: Getting Started with "Kotlin" on Android App Development


To put it in a nutshell, for general purpose programming, Java is beneficial. On the other side, more and more Android App Development Companies are adopting Kotlin for the rapid pace development. The above discussion is saying both have their own advantages over others. The debate about which of them is greatest will go on, and not reaching any conclusion any time soon.

About Us:

As a full service custom mobile app development company, Kunsh Technologies believes that, if you’re a developer then you need to upgrade your skills to the latest trends. Our experienced Android App Developers are proficient in each vertical and trained to deliver on time splendid Android Apps. If you have an amazing idea to develop your android app, get in touch with our team. We will help you build the best Android Apps that will help you boost your business.