What Should You Use for Your Next Project: Kotlin or Java?

There has been much debate in the development community as to whether Kotlin or Java is the superior language. To help address this question, a poll was conducted which revealed that 36% of developers are currently using Java, while only 8% are utilising Kotlin. Java has been a widely used programming language for mobile and web applications for the past two decades. In contrast, Kotlin is the official programming language for Android app development, as endorsed by Google. It is clear that, while Java is the more widely used language, Kotlin is becoming increasingly popular in the development community due to its versatility and use in Android development. In order to decide which language is the superior choice, it is important to analyse the advantages and disadvantages of both Java and Kotlin.

Kotlin is a programming language that combines aspects of both object-oriented and functional programming, making it a versatile option for developers. Popular applications built with Kotlin include Netflix, Uber, Tinder, Airbnb and Pinterest. Java, on the other hand, is an object-oriented programming language and notable applications built with this language include Twitter, Spotify, and LinkedIn.

Is Kotlin a replacement for Java?

Kotlin is quickly becoming the preferred language for Android development due to its user-friendly characteristics. Despite its growing popularity, Kotlin cannot replace Java, a widely-used programming language. Millions of developers around the world still rely heavily on Java for their projects, making it clear that this legacy language is far from obsolete.

Is it difficult to learn Kotlin?

Kotlin is an approachable programming language which is easy to comprehend; however, those who wish to become proficient in Kotlin should first gain a thorough understanding of the fundamentals before exploring the various design and syntax features the language has to offer. Those with prior knowledge of Python or Java should find it easier to learn Kotlin.

Let’s look at the fundamental distinctions between Java and Kotlin:

  1. Extension functions in Kotlin vs. Java

    Extension functions are not available in Java. To add this feature, developers must create a new class and parent class.

    Kotlin facilitates developers in creating extension functions for existing classes with ease. To enable the usage of extension functions, developers must prefix the class and function name.
  2. Implicit conversion between Kotlin and Java

    Implicit type conversion is a process in which a compiler automatically converts a data type to another. In Java, there are seven different data types. Data types of the same type can be automatically converted into larger data types in order to accommodate smaller data types. This functionality is enabled in Java through implicit type conversion.

    Because Kotlin does not provide implicit data type conversion, smaller data types do not convert to bigger data types.
  3. Data classes in Kotlin vs. Java

    Kotlin provides an efficient way of constructing data classes by enabling developers to declare them using the keyword ‘data’. Upon doing so, the Kotlin compiler automatically generates the constructor, getter and setter methods for the class, thus saving the developers from having to write them manually.

    To create data classes, developers must define the constructor, getter, and setter methods in Java.
  4. Language scripting in Kotlin vs. Java

    Language scripting enables developers to automate the execution of certain functions that would otherwise require manual intervention.

    Language scripting can be integrated into existing Kotlin scripts, however, Java does not support language scripting.
  5. Operator Overloading in Kotlin vs. Java

    Operator overloading is a programming language feature which allows the same operator to be used with multiple data types. Specifically, the same operator can be used to perform different operations depending on the type of the data it is being used with. An example of this is the + operator, which can be used for addition in numerical data types and for concatenation in string data types. Unfortunately, Java does not support operator overloading with the exception of the + operator.

    Kotlin enables developers to utilise the precedence of a predetermined collection of operator types, including the plus and multiplication symbols. In order to implement operator overloading, programmers must define the associated type’s corresponding member function with a precise name.
  6. Static members in Kotlin vs. Java

    Java utilises static members to manage memory. By utilising the static Java keywords, developers can make methods, blocks, variables, and nested classes static members, allowing them to be accessed without requiring the class to be instantiated.

    Kotlin does not use static variables in name fields, unlike other programming languages. To construct a companion object within the class, developers must utilise the Kotlin object feature. This companion object acts as a static member, providing direct access without interfering with the containing class, since it is a single entity.
  7. String templates and expressions in Kotlin vs. Java

    String templates in Java are an assortment of string literals which, when used, will produce a sequence of characters that is visible to the user. These string literals are encased within quotation marks and do not support the use of expressions.

    Kotlin has two types of string templates: raw strings and escape string templates. These templates enable the inclusion of expressions within strings, which can then impact the outcome of a pre-existing program.
  8. Smart cast in Kotlin vs. Java

    Smart casting is an advantageous feature of the Kotlin programming language which allows developers to track an object or variable and safely cast it into the relevant types and methods. This allows developers to avoid manually casting objects, thus saving time and effort when coding. Furthermore, it helps ensure the accuracy of the code and reduces the chances of errors occurring.

    Due to the lack of smart casting capability in Java, developers are required to perform two separate operations. The initial step involves verifying the type of the variable, followed by casting the object to the desired type.
  9. Type inference in Kotlin vs. Java

    Type inference is a feature of some programming languages that allows for the automatic deduction of data types, such as integer, character, or Boolean, for specified phrases. Unfortunately, the Java programming language does not provide type inference capabilities, meaning that developers must specify the data type of each variable prior to declaring it.

    Kotlin supports type inference, which eliminates the need for developers to declare the type of each variable individually.


Kotlin is a modern programming language developed with Java in mind and with a specific focus on Android development. Its concise syntax enables developers to write more efficient code, with fewer lines, compared to Java and other languages. However, when it comes to developing client-side and web applications, many developers still prefer to use Java.

In conclusion, developers should select a programming language that best meets the requirements of their project, taking into account the advantages and disadvantages of each language to ensure an informed decision.

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