Scala vs. Kotlin: Choosing the Right JVM Language

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Scala vs. Kotlin: Choosing the Right JVM Language

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May 3rd, 2024

Scala and Kotlin are modern JVM languages that run on the Java Virtual Machine. They offer developers an alternative to Java that provides more concise and expressive syntax while still having access to the large ecosystem of Java libraries.

Scala emerged in the early 2000s as a multi-paradigm language that blended object-oriented and functional programming concepts. Kotlin was created in 2011 by JetBrains as a response to complaints about Java’s verbosity. It takes inspiration from languages like Scala, Groovy, and C# to provide a more concise and safe programming experience.

While Scala vs. Kotlin have similarities, they take different approaches in areas like syntax, functional programming support, and compilation. This leads to trade-offs for any custom website development firm to consider when choosing between the two. 

This article will get into the details to understand where each language shines and help guide the decision between Scala vs. Kotlin.

Language Syntax

Scala vs. Kotlin have similar syntax as they both run on the JVM. However, there are some key differences:

  • Scala uses a mix of object-oriented and functional programming styles. The syntax can be complex with lots of special characters like {}, (), [], etc. Kotlin aims for simplicity and readability in its syntax, avoiding too many special characters and symbols.
  • Scala is more verbose, and Kotlin aims to reduce boilerplate code. For example, getters and setters are implicit in Kotlin but must be explicitly defined in Scala.
  • Scala relies heavily on immutable values and functional constructs like higher-order functions. Kotlin also supports functional programming but provides more flexibility for mutable states when needed.
  • Scala has significant white space dependence and uses curly braces to denote code blocks. Kotlin uses semicolons to end statements and avoids white space dependence.
  • Kotlin introduces new concepts like extension functions and null safety. Scala doesn’t have built-in null safety but offers Options for similar functionality.

Functional Programming

Both Scala and Kotlin support functional programming constructs like higher-order functions, immutable data structures, and pattern matching.

Scala fully supports functional programming, designed to integrate object-oriented and functional paradigms. Its features include currying, tail recursion, lazy evaluation, and pattern matching.

Kotlin also supports many functional programming concepts but doesn’t go as far as Scala in this regard. It has first-class functions, lambda expressions, higher-order functions, and support for immutability. But it lacks advanced FP features like currying or lazy evaluation.

A key difference is that Kotlin only allows immutability for local variables, while Scala has immutable collections in its standard library. Kotlin’s support for functional programming is more geared towards enabling a hybrid OOP/FP style rather than being a fully-fledged functional language.

Scala has much more complete support for purely functional programming, while Kotlin takes a lighter approach.

Object Oriented Programming

Both Scala vs. Kotlin provide excellent support for object-oriented programming (OOP).

Scala is built on the Java Virtual Machine (JVM) and fully interoperates with Java. It has a sophisticated type system and supports most Java features like classes, interfaces, inheritance, polymorphism, abstract classes, etc. 

However, Scala also improves Java’s OOP model by adding constructs like traits, mixins, and universal traits. This allows for greater code reuse through composition. Scala also supports pattern matching on types and other advanced OOP features.

Kotlin was designed from the ground up to be fully interoperable with Java. It has first-class support for classes, interfaces, inheritance, abstract classes, and all other basic OOP constructs. 

Kotlin improves upon Java with features like data classes, sealed classes, nested classes, extension functions, and more. It provides a concise syntax to reduce boilerplate code compared to Java. Kotlin’s smart casts and other features also help make code safer.

Overall, both languages stand out in app development tools, offering tailored approaches to OOP: Scala with its profound type system and progressive features and Kotlin with its pragmatic enhancements to Java’s model.

Tooling and IDE Support

Both Scala vs. Kotlin have excellent tooling and IDE support available.

The most popular IDE for Scala is IntelliJ IDEA, which has excellent Scala support through the Scala plugin. This provides features like code completion, debugging, refactoring, and more for Scala development. 

For Kotlin, IntelliJ IDEA is also the recommended IDE, as JetBrains developed Kotlin. It has built-in Kotlin support, including all the expected features. 

Scala vs. Kotlin has exceptional tooling available in IntelliJ IDEA and through build tools like SBT and Gradle. For most developers, the IDE and build tool experience will be similarly excellent with both languages. The availability of high-quality tooling and IDE support is a strength of both Scala and Kotlin.


When it comes to performance, both Scala and Kotlin perform well on the JVM. Nonetheless, The App Founders developers note some distinctions worth considering by others as well.

  • Runtime performance

Scala and Kotlin have similar runtime performance that is on par with Java. The JVM optimizes and compiles bytecode for all three languages similarly. However, Scala can perform slightly slower in some cases due to features like implicit and higher-order functions that lead to more complex bytecode.

  • Compile speeds

Kotlin has significantly faster compile times compared to Scala. This is because Kotlin’s compiler was designed from the ground up to have fast incremental compilation. Scala compile times worsen for larger codebases due to complex type checking and implicit conversions.

  • Startup times 

Again, Kotlin has an advantage regarding startup times and cold starts. The Kotlin compiler generates more lightweight and optimized bytecode that is faster to initialize at runtime. Scala has slower startup times due to JVM classloading and initialization of complex types.

  • Memory usage 

Kotlin tends to have lower memory usage compared to Scala code. Features like inlining help reduce the number of classes and memory needed to run Kotlin code. Scala’s more complex types can lead to more classes and higher memory utilization.

Therefore, Kotlin generally has faster compilation, startup times, and lower memory usage than Scala due to its more optimized compiler and lightweight bytecode generation. However, both languages have comparable runtime performance on the JVM once the code is compiled and running.


Scala vs. Kotlin are both modern JVM languages that improve upon Java in many ways. However, they take different approaches, and each has its strengths.

Scala shines with its robust functional programming and complex type system, making it a powerhouse within development frameworks. Kotlin is designed to be simpler and more pragmatic. 

If you need maximum power and expressiveness for complex applications involving big data, math, or finance, Scala may be the better choice. For general-purpose development focusing on Android, or if you value simplicity, Kotlin is likely the preferable option. Both move the JVM language ecosystem forward in meaningful ways.

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