Kotlin vs Java: Which One is Better?

Romana Hoekstra
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Kotlin vs Java: Which One is Better?

Kotlin is a statically-typed programming language developed by JetBrains in 2011. Its main goals are to be more concise and safer than Java. On the other hand, Java has been around for over two decades and is known for its portability, scalability, and security.

The debate between Kotlin and Java has been ongoing for several years, with developers arguing about the strengths and weaknesses of each language. Some prefer Kotlin's concise syntax and powerful features, while others believe Java's stability and robustness make it the superior option.

In this blog post, we'll explore the syntax and features of Kotlin and Java and their performance, productivity, community, adoption, and use cases. By the end of this post, you'll better understand each language's strengths and weaknesses and be better equipped to choose the best language for your next project. Let's dive in!

Origins of Java and Kotlin

Kotlin and Java have different origins that have influenced their design and development.

Kotlin was developed by JetBrains, a software development company based in St. Petersburg, Russia. The language was initially designed to address some of Java's shortcomings and improve developer productivity. JetBrains released Kotlin as an open-source language in 2012, and it has since gained popularity among developers for its simplicity and powerful features.

Java was developed by James Gosling and his team at Sun Microsystems in the early 1990s. The language was designed to be portable, secure, and scalable, and quickly gained popularity for its use in web development. In 2009, Sun Microsystems was acquired by Oracle Corporation, which has continued to develop and maintain the language.

While Kotlin and Java are object-oriented and share some similarities in syntax and features, their origins have influenced their development and design decisions. Kotlin was specifically designed to address some shortcomings of Java, such as null safety and verbosity. At the same time, Java's long history and widespread adoption mean it has a larger and more established ecosystem.

Features of Java vs Kotlin


Java is a programming language widely used for developing various applications for many years. Here are some of its notable features:

  • Checked exceptions: Java has a "checked exceptions" feature that ensures that exceptions are caught or declared by the calling method. This feature helps improve the code's reliability but can also make it more complex.
  • Primitive types that are not classes: Java has primitive data types such as int, float, and boolean, which are not represented as objects. The bytecode uses primitives wherever possible but are not explicitly available as objects. This feature helps improve performance by reducing the memory footprint and overhead of the program.
  • Static members are replaced with companion objects, top-level functions, extension functions, or @JvmStatic: Java has static members, which can be accessed without creating an instance of a class. In Kotlin, static members are replaced with companion objects, top-level functions, extension functions, or @JvmStatic annotations. This feature helps in reducing boilerplate code and improving readability.
  • Wildcard-types are replaced with declaration-site variance and type projections: Java has wildcard types that express unknown types. In Kotlin, wildcard types are replaced with declaration-site variance and type projections. This feature allows for more precise type inference and safer code.
  • Ternary-operator a ? b : c is replaced with if expression: Java has a ternary operator, which is used to simplify if-else statements. In Kotlin, the ternary operator is replaced with if expressions. This feature allows for more concise code and reduces redundancy.
  • Maturity: Java has been used in many large-scale projects and has proven to be a reliable and stable programming language. This means that Java is often considered a safe choice for enterprise-level projects.

Overall, Java has many useful features that make it a powerful and popular programming language. Its features, such as checked exceptions, primitive data types, and static members, make it well-suited for developing large-scale and enterprise applications.


Some features of Kotlin are:

  • No raw types: Kotlin does not allow raw types, which improves type safety and reduces the risk of runtime errors.
  • Arrays in Kotlin are invariant: Kotlin's type system treats arrays as invariant, preventing errors that could occur with covariant or contravariant arrays.
  • Null-safety: Kotlin's null-safety features ensure that null references are caught at compile-time, reducing the risk of runtime errors.
  • String templates: Kotlin's string templates make it easy to interpolate values into strings, reducing the boilerplate code required.
  • Properties: Kotlin's properties allow for more concise and readable code, replacing Java's traditional getters and setters.
  • Declaration-site variance & Type projections: Kotlin's variance and type projection features provide more flexible type handling and reduce the need for explicit casting.
  • Companion objects: Kotlin's companion objects provide a way to associate functionality with a class without needing static members.
  • Separate interfaces for read-only and mutable collections: Kotlin's standard library provides separate interfaces for read-only and mutable collections, making code more concise and less error-prone.

Kotlin vs Java Performance

Kotlin has significantly improved its performance over the years, and in some cases, it can outperform Java. For example, Kotlin's support for inline functions and reified type parameters can help eliminate some overhead associated with generic types. In terms of memory usage, Kotlin typically uses less memory than Java due to its more efficient handling of null values and the use of immutable data structures.

Java has traditionally been faster than Kotlin in terms of raw performance due to its more established optimisation techniques and mature ecosystem. However, the difference in performance is often negligible in real-world applications.

Ultimately, the performance of Kotlin and Java will depend on the specific requirements of your application and the trade-offs between performance, maintainability, and developer productivity. Benchmarking and profiling your code regularly is important to identify performance bottlenecks and optimise your application for the best possible performance.

Productivity of Kotlin vs Java

Productivity is an essential consideration when choosing a programming language, as it can significantly impact the final product's development time and quality.

Kotlin was designed with developer productivity in mind, offering several features to make developers more productive. For example, Kotlin's concise syntax and type inference can help reduce boilerplate code, while its null safety features can help prevent NullPointerExceptions, a common source of errors in Java.

Kotlin also has excellent support for functional programming constructs, which can help make code more concise and expressive. Additionally, Kotlin's interoperability with Java means that developers can use existing Java code and libraries seamlessly, making it easy to migrate from Java to Kotlin.

On the other hand, Java has a more mature ecosystem and a larger community, which means it has a broader range of tools, frameworks, and libraries available. This can make development more efficient, as developers can leverage these resources to build applications quickly.

Use cases of Java

  • Enterprise applications and web development: Java is widely used for developing enterprise applications such as financial systems, e-commerce platforms, and inventory management systems. It is also a popular choice for web development, with frameworks such as Spring and Struts providing support for building web applications.
  • Developing Android applications using the Android SDK: Java is the primary language used for developing Android applications using the Android SDK, which provides a rich set of libraries and tools for building mobile apps.
  • Developing server-side applications using frameworks such as Spring and Hibernate: Java is commonly used for building server-side applications, with frameworks such as Spring and Hibernate providing support for building web services, RESTful APIs, and other server-side applications.
  • Building large-scale applications with high-performance requirements: Java's performance and scalability make it a good choice for building large-scale applications that require high performance and reliability, such as trading systems, airline reservation systems, and telecom billing systems.
  • Developing desktop applications using JavaFX: JavaFX provides tools and libraries for building desktop applications, making Java a good choice for developing applications such as trading platforms, CAD software, and data visualisation tools.
  • Developing scientific and engineering applications: Java is used for developing scientific and engineering applications that require high-performance computing and complex algorithms, such as simulations, data analysis, and image processing.

Use cases of Kotlin

  • Android app development, particularly for its Android-specific features and compatibility with Java: Kotlin is a popular choice for developing Android applications due to its concise syntax, null safety features, and Android-specific extensions such as Anko and KTX.
  • Server-side development using frameworks such as Ktor and Spring: Kotlin can be used for building server-side applications, with frameworks such as Ktor and Spring supporting web services and RESTful APIs.
  • Cross-platform development using Kotlin Native: Kotlin Native allows developers to write Kotlin code that can be compiled to native binaries, making it possible to build cross-platform applications for desktop, mobile, and embedded devices.
  • Developing reactive and event-driven applications using Kotlin's support for functional programming concepts: Kotlin's support for functional programming concepts such as higher-order functions, makes it a good choice for developing reactive and event-driven applications, such as those that handle real-time data streams or asynchronous events.
  • Building tools and plugins for development environments such as IntelliJ IDEA: Kotlin's interoperability with Java and its support for DSLs (domain-specific languages) make it a good choice for building tools and plugins for development environments such as IntelliJ IDEA.

Future of Java and Kotlin

Both Kotlin and Java are expected to continue to evolve and improve. Java 17 will be released new features like pattern-matching instances and records. Kotlin, on the other hand, is expected to continue to expand its capabilities and ecosystem with improved support for multiplatform development and enhanced tooling.

The future outlook for Java and Kotlin will likely continue to affect their use differently. As Java continues to evolve and improve, it may become an even more attractive option for enterprise and large-scale applications. Kotlin's focus on multiplatform development and functional programming may make it more attractive for cross-platform development and emerging application architectures.

We may see a continued trend towards multiplatform development and functional programming concepts soon. This could lead to increased use of Kotlin and other languages that support these trends. Additionally, the rise of artificial intelligence and machine learning could lead to increased use of languages such as Python and R for data analysis and modelling. However, Java's continued popularity and strong community support suggest that it will remain a widely-used language in the foreseeable future.

Key differences between Java vs Kotlin

Let’s summarise of differences between Kotlin and Java.

  • Syntax: Kotlin has a more concise and expressive syntax than Java. This means less code is required to achieve the same functionality in Kotlin.
  • Null Safety: Kotlin has built-in null safety features, making it less prone to NullPointerException errors than Java.
  • Functional Programming: Kotlin has better support for functional programming concepts such as lambdas and higher-order functions, while Java only added these features in its recent versions.
  • Interoperability: Kotlin is fully interoperable with Java, which means that Kotlin code can interact with Java code seamlessly. However, the reverse is not always true.
  • Learning Curve: Kotlin is easier to learn and use than Java, making it a better choice for beginners and small projects.
  • Community: Java has a larger community and a wider range of libraries and frameworks than Kotlin, so more resources and solutions are available for Java developers.

Final thoughts

Java is a mature language used for enterprise applications, web development, Android app development, and large-scale applications. At the same time, Kotlin is a modern language well-suited for developing Android, server-side, cross-platform, reactive, and event-driven applications and tools and plugins for development environments.

Kotlin is a strong choice for Android app development due to its compatibility with Java and Android-specific features.

  • For server-side development, both Java and Kotlin are viable options, with Java being a safer choice for larger and more complex applications.
  • For cross-platform development, Kotlin Native is a promising option, but still relatively new compared to other cross-platform frameworks.
  • For desktop applications and tools/plugins development, Java remains a solid choice due to its strong community and ecosystem.

Ultimately, the choice between Kotlin and Java will depend on the project's specific needs and the developer's experience and preferences.


  1. Is Kotlin better than Java?

    It depends on the specific use case and the preferences of the developer. Kotlin offers some advantages over Java regarding syntax, null safety, extension functions, and support for functional programming concepts. However, Java has a larger community and ecosystem, making it a safer choice for large-scale and enterprise applications.

  2. Will Kotlin replace Java in the future?

    It is unlikely that Kotlin will completely replace Java in the foreseeable future. Java has a strong community and ecosystem and is widely used for large-scale and enterprise applications. However, Kotlin may continue gaining popularity and be used more frequently for certain applications.

  3. Should I learn Kotlin or Java?

    This depends on your goals and the specific needs of your project. If you are interested in Android app development, then learning Kotlin would be a good choice, as it is the preferred language for Android development. If you are interested in enterprise applications or large-scale development, learning Java is a safer choice due to its larger community and ecosystem. Learning both languages may be beneficial, as they have different strengths and use cases.

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