Kotlin vs Java: Which is more suited for Android app ...
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Kotlin vs Java: Which is more suited for Android app development?

Published datePublished: Jan 21, 2020 ViewsViews: 4404
Shanal Aggarwal

Shanal Aggarwal

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Shanal is a passionate advocate for crafting innovative solutions that address real-world challenges and consistently deliver outstanding results for TechAhead's clients. As a strategic and creative leader, he specializes in driving revenue expansion, developing client-focused solutions, pioneering product innovations, and ensuring seamless program management.
Kotlin vs Java: Which is more suited for Android app development?

Kotlin vs Java

A programming language is a formal language that produces various kinds of outputs by making use of a particular set of instructions. Ever since the discovery of programming languages, many of them have been created and the number is increasing every year.

Some programming languages are written in an imperative form that follows a sequence of operations to be performed in order to get the output while others use a declarative form in which the desired output is specified but not the methods to obtain it. Swift, Go, Dart, Java, C, Python, and many other programming languages are widely used by app developers. As per StackOverflow, Kotlin is the most wanted language as compare to Java.

Most Loved Programming Languages

Kotlin and Java are preferred more over other programming languages. Let’s try to understand why:

Kotlin: A programming language for JVM, Android, Browser, Native

Kotlin was created by JetBrains and was announced as the second official language of Android app development at the Google I/O. It’s in a steady partnership with Google cloud platform, Spring framework, and Gradle and it’s believed to make the process of Android application development faster while growing continuously. Leading tech companies are hiring app developers who are well versed in Kotlin and it’s coming out to be one of the most employment sectors as it’s open-source.

Other benefits include the usage of existing Java Framework and Libraries by the programs that are written using Kotlin, a compilation with JVM bytecode or JavaScript, easy to learn and approachable methodology, great null safety, automatic conversion of Java to Kotlin, and the ease of reviewing the codes.

Java: Write once, run anywhere (WORA)

Java was developed by Sun Microsystems and can be used to create any type of program as it’s compatible with almost every kind of machine and operating systems such as Windows or Linux. Java has one of the biggest and most important and largest communities in the world.

It has a great potential of solving critical issues with its benefits which include ease of learning, providing the users with an independent platform, the facility to create modular programs and reusable code, network-centric programming, high-security features and efficiency, robust and dynamic nature and user-friendly experience.

Kotlin vs Java: Understand the distinction between the two programming languages

Java is an object-oriented programming language and programs, or applications developed in Java and execute in JVM by which it can run the same program on multiple platforms or devices i.e. write once, run anywhere. While Kotlin is a new programming language that handles some modern features and it’s a statically defined language.

Some Java issues addressed in Kotlin

Every programming language suffers from certain issues and Java is no stranger to such issues. It has some issues associated with it that can be resolved using Kotlin such as:

  • Null references are controlled by the type system: Accessing a member of a null reference is always a problem in many programming languages including Java as it results in a null reference exception. Kotlin solves this issue by controlling the null references by the type system.
  • No raw types: Kotlin allows interoperability with Java and existing Java code can be called from Kotlin in a natural way.
  • Arrays: In Kotlin, arrays are in-variant while in Java they are co-variant. The in-variant nature of arrays prevents run-time failures.
  • Proper function types: Kotlin uses a family of function types for declarations that deal with functions, unlike Java’s SAM conversion.
  • Wildcards: It uses declaration site variance that allows smooth communication between the compiler and the user.
  • Checked exceptions: Kotlin doesn’t have checked exceptions as every exception has a message, stack trace, and an optional cause.

What Java has that Kotlin does not?

Java is not only about issues and drawbacks. There are many benefits and unique features associated with it that set it apart from all other programming languages which include: 

  • Checked exceptions: Java has checked exceptions while Kotlin doesn’t i.e. you don’t need to IO Exceptions every time to append a string to something.
  • Primitive types: These don’t have any inheritance relation to the array class, but they follow the same methods and properties. They all have a corresponding factory function as well.
  • Static members: It’s a way of grouping various classes in Java. Only nested classes are allowed in Java.
  • Non-private fields: Fields are normal variable members of a class. Java makes use of non-private fields as private fields can only be accessed inside a class.
  • Wildcard-types: By using the wildcard type of argument the acceptance of collections of similar sub-type becomes easier.
  • Ternary-operator: It functions more like a Java if statement based on a condition to evaluate a value on the basis of the logical condition provided.

What Kotlin has that Java doesn’t?

Both languages offer a wide variety of features but why Kotlin is considered as a competition for Java even when it’s a newer language? Let’s understand this by looking at some of the features provided by Kotlin that Java doesn’t:

  • Extension functions: Kotlin allows the extension of a class without inheriting it from the class or using design patterns. It’s achieved by special declarations called extension functions.
  • Null safety: It eliminates the danger of null references from the code, known as “The Billion Dollar Mistake”. 
  • Smart casts: They are applicable for local delegated properties and local variables if the variable is not modified between the check and usage.
  • String templates: Strings are immutable characters that can be accessed by the indexing operation. String literals often consist of template expressions which are nothing, but pieces of code used to evaluate the result. The expression of a template starts with a dollar sign.
  • Primary constructors: They are a part of the class header. It goes after the class name and parameter types that are optional. Primary constructors can’t contain any code.
  • First-class delegation: It’s used to implement inheritance and it’s supported by Kotlin needing zero boilerplate code. 
  • Type inference for variable and property types: In Kotlin, everything is an object and we can call member functions and properties on any variable.
  • Singletons: Sometimes, without declaring a new subclass explicitly, we need to create an object with a slight modification of some class. Such a case is perfectly handled by Kotlin with object expressions and object declarations.
  • Declaration-site variance & Type projections: These are used when we have a generic interface that doesn’t have any input methods but can produce output only.
  • Range expressions: These are defined for comparable identities to define whether an arbitrary instance is in the given range.
  • Operator overloading: Using Kotlin, one can implement a predefined set of operators that have fixed symbolic representation. The functions that overload the operator are marked with the operator modifier.
  • Companion objects: By declaring companion objects inside your class, its members can be accessed only by using the class name as a qualifier.
  • Data classes: Classes with standard functionality and utility functions are mechanically derivable from the data known as data class in Kotlin and marked as data.
  • Separate interfaces for read-only and mutable collections: The Kotlin Standard Library provides a comprehensive set of tools for managing collections that share significance to the problem being solved and are operated upon commonly.
  • Coroutines: It’s helpful in realizing the asynchronous or non-blocking programming to provide a fluid and scalable user experience.

Also Read:
Why unicorns prefer Kotlin for Android app development?

Kotlin vs Java: Comparison at a glance

Feature Java Kotlin
Checked Exceptions Available Unavailable
Coroutines Unavailable Available
Data Classes Required to write a lot of boilerplate code Requires adding only the data keyword
in the class definition
Extension Functions Unavailable Available
Non-private Fields Available Unavailable
Smart Casts Unavailable Available
Static Members Available Unavailable
Ternary Operator Available Unavailable
Wildcard Types Available Unavailable
Extension Functions Unavailable Available
Inline Functions Unavailable Available

Still not confident? Here’s the solution

From the above-made comparison between Kotlin and Java, we can clearly see that Kotlin has got an upper hand as it’s growing continuously every day. It has better features than Java such as compatibility, security, syntax and functional programming. It’s proving to be the pragmatic, modern, and intuitive language for Android app developers that they’ve been waiting for. However, it all depends on preferences and Java is more widely used than Kotlin as it’s trusted more by the users.

Irrespective of all the differences between the two programming languages, Kotlin and Java, are fully interoperable. Both languages compile to bytecode eventually thus making it possible to call Java code from Kotlin and vice-versa. This flexibility has many advantages out of the two are dominant. First, it helps developers to kick-start by incrementally introducing Kotlin in a Java project. Second, both the programming languages can be used simultaneously in any Android application development project.


Nevertheless, it’s a newer language as compared to Java while Java has already made its place in the market. Kotlin is demonstrating its worth at a great pace and proving that it is a superior programming language for mobile app development by offering developers a lot of opportunities to experiment with modern programming. It allows the developers to make the transition between OO, FP, scripting and declarative paradigms without any effort and ease of establishing a new standard for what a programming language should be able to achieve.

Frequently Asked Questions (FAQs)

Is Kotlin better than Java?

Kotlin has a steep learning curve and beats Java in many cases. However, there are some features and fields in which Java is superior.

Should I learn Java before Kotlin?

Kotlin is a newer language that makes use of the platforms developed for Java, but it can stand on its own. There is no need to learn Java before Kotlin.

Which language is best for Android app development?

Java is the most widely used and the official language for Android app development.

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