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Kotlin vs Java: Which one to choose?

For Developers, Kotlin and Java have appeared as well-known players, captivating their attention worldwide. As the demand for robust and efficient software solutions continues to zoom, the age-old question arises: Kotlin vs Java? Which one should you choose for your next project?

Both Kotlin and Java possess their own unique strengths and cater to various programming needs. To make an informed decision, it is crucial to understand their key features and weigh the advantages they offer. In this article, we'll explore the difference between Kotlin and Java, providing Advantages, Disadvantages, differences, and key factors that can influence your decision.

What is Kotlin?

Kotlin is a universal programming language with an open-source nature. It combines object-oriented and functional programming paradigms and offers seamless compatibility with Java. One of Kotlin's notable features is its concise syntax, which enhances code readability and writability.

This modern language serves as a general-purpose tool and finds applications in various domains, including web development and Android app development. Its flexibility makes it suitable for a wide range of projects and use cases.

Kotlin has the ability to be compiled into different output formats. Besides being executed on the Java Virtual Machine (JVM), Kotlin code can also be compiled into JavaScript, allowing developers to build client-side web applications. Additionally, Kotlin can be compiled into native code using LLVM, enabling the creation of high-performance applications that can run directly on the target platform.


  1. Compatible with existing Java Code and interoperable with Java Libraries.

  2. It has a concise and expressive syntax that reduces boilerplate code.

  3. Supports null safety, extension functions, data classes, coroutines, and other features that make coding easier and safe.

  4. Supports functional programming with higher-order functions and lambdas.


  1. Less stable than Java, few tools and resources are available.

  2. Slow compilation speed

  3. May have compatibility issues with older Android devices.

What is Java?

Java is a widely-used programming language known for its high-level, object-oriented nature. It follows a class-based approach and is designed to minimize dependencies on specific implementations. This feature allows Java code to be portable across different platforms.

As a general-purpose language, Java aims to enable developers to write code once and run it anywhere. This concept is achieved through the Java Virtual Machine (JVM), which serves as a platform-independent execution environment. Once Java source code is compiled, it produces bytecode that can be executed on any JVM, regardless of the underlying computer architecture or operating system.

The bytecode generated by the Java compiler provides a level of abstraction that allows Java applications to be platform-neutral. This means that compiled Java code can run on diverse computing platforms, such as Windows, macOS, Linux, and more, as long as a compatible JVM is available.

The ability to write platform-independent code and the widespread adoption of the JVM have contributed to Java's popularity and versatility. Java has been used to develop a wide range of applications, including web and enterprise systems, mobile apps, scientific software, and embedded systems.


  1. Widely used and supported by the developers.

  2. Robust and performant. Huge set of libraries and frameworks.

  3. Supports checked exceptions, primitive types, wildcard types, and other features that make coding flexible.

  4. Supports ternary operator, static members, and implicit widening conversions that make coding more convenient.


  1. The repetitive syntax requires more code to achieve the same functionality as Kotlin.

  2. Prone to null pointer exceptions and other runtime errors that can crash the application.

  3. Does not support some of the modern features that Kotlin offers, such as coroutines, data classes, extension functions, etc.

Difference: Kotlin vs Java

Below we have a difference between Kotlin and Java, which may help to select the particular programming language for specific purpose:






Object-oriented and functional Programming


class HelloWorld { public static void main(String[] args) { System.out.println("Hello, World!"); } }

fun main(args: Array<String>) { println("Hello, World!") }

Null Safety

Prone to null pointer exceptions

Supports nullability annotations and null checks

Functional Programming

Supports Lambda expression, higher order functions and extension functions.

Supports Lambda expressions (since Java 8)


Slightly slower in some cases

Slightly faster in some cases

Extension Functions

Java does not offer any extension functions

Allows users to create extension functions, which can add new functionality to an existing class without modifying its source code

Implicit Conversions

Supports implicit conversions which can sometimes lead to unexpected results or errors.

Does not support implicit conversions which means that the compiler will not automatically convert one type to another without explicit casting.

Smart Casts

Does not support smart casts, which means that the developer has to manually cast the variable to the desired type.

Supports smart casts, which means compiler can automatically cast a variable to a specific type if it is immutable and had been checked for that type.

Type Inference

Does not support type inference. The developer has to specify the data type of every variable explicitly.

Supports type inference. The Developer does not have to specify the data type of a variable explicitly if it can be inferred from the context.

Compilation speed

Faster than Kotlin

Slower than Java especially in incremental builds

Learning curve

Hard to learn but has few complex features

Easier to learn but has some complex features


Java is widely preferred to used as compared Kotlin

It is popular among android developers


1. Android mobile apps 2. Web Applications 3. Cloud-based Applications 4. Smart Devices and IoT 5. Enterprise Applications 6. Desktop Applications

1. Back-end Web Development 2. Full Stack Web Development 3. Data Science 4. Multi-platform Mobile Development 5. Smart Devices and IoT 6. Android Mobile Apps

Which one to choose: Java or Kotlin

When selecting between Java and Kotlin for a project, various project requirements come into play. Some of these requirements are as follows:

1. Android development: Kotlin is the preferred language for Android development as it is officially supported by Google and offers numerous features that enhance coding efficiency and speed for Android applications. Kotlin provides better support for coroutines, which are beneficial for writing asynchronous and non-blocking code on the Android platform. However, Java is still widely used for Android development due to its extensive library and resource availability, as well as potential better compatibility with older Android devices.

2. Web development: Both Java and Kotlin can be used for web development as they run on the Java Virtual Machine (JVM) and can leverage frameworks like Spring Boot or Micronaut. However, Kotlin offers certain advantages over Java, including concise and expressive syntax, null safety, extension functions, and data classes. Additionally, Kotlin can be compiled into JavaScript or native code via LLVM, potentially providing improved performance and portability.

3. Legacy code: If a project already contains a significant amount of existing Java code, it may be more convenient to stick with Java rather than transition to Kotlin. However, Kotlin is fully compatible with existing Java code and supports interoperability with Java libraries. This means it is possible to gradually migrate from Java to Kotlin or even combine both languages within the same project. Furthermore, there are tools available to assist in automatically or semi-automatically converting Java code to Kotlin.

Ultimately, the choice of language may be influenced by the preference and experience of the developer. Some developers may favor Java's verbose and explicit syntax, while others may prefer Kotlin's concise and expressive syntax. Familiarity and comfort with a particular language can also play a role in the decision-making process. Additionally, factors such as the learning curve, documentation, community support, and tooling can influence a developer's preference for one language over the other.



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