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

The debate within the development community as to whether Kotlin or Java reigns supreme has been ongoing. However, according to a recent poll, Java is currently utilised by 36% of developers, while only 8% opt for Kotlin. Java has been the go-to programming language for mobile and web applications for the past 20 years, whereas Kotlin is the endorsed programming language for Android app development by Google. While Java is more widely used, Kotlin’s versatility and use in Android development is leading to its increasing popularity. To determine which language is superior in the end, it is important to consider the advantages and disadvantages of both Java and Kotlin.

Developers can benefit from the versatility offered by Kotlin, a programming language that blends object-oriented and functional programming. Major brands including Netflix, Uber, Tinder, Airbnb and Pinterest have implemented Kotlin into their development processes. Meanwhile, Java is solely an object-oriented programming language and has been used by notable companies like Twitter, Spotify, and LinkedIn to create their applications.

Can Kotlin replace Java?

Thanks to its user-friendly traits, Kotlin is gaining popularity as the preferred programming language for Android development. However, despite its rising popularity, Kotlin cannot replace Java – a widely utilised programming language that millions of developers worldwide continue to depend on heavily for their projects. This indicates that the legacy language is far from becoming obsolete.

How challenging is it to learn Kotlin?

Kotlin is a beginner-friendly programming language that’s easy to understand. However, those who want to become adept in Kotlin need to acquire a solid grounding in the fundamentals before exploring the language’s diverse design and syntax features. Especially those who have previous experience in Python or Java should have an easier time learning Kotlin.

Now, let’s examine the basic differences between Java and Kotlin:

  1. Extension functions in Kotlin vs. Java

    Unlike Java, extension functions aren’t supported in Java. Therefore, adding this feature entails developers creating a new class and parent class. However, Kotlin allows developers to generate extension functions for existing classes seamlessly. To use extension functions, developers just need to add a prefix to the class and function name.
  2. Implicit conversion between Kotlin and Java

    One of the compiler’s automatic processes is known as implicit type conversion, which refers to the conversion of one data type to another. In Java, there are seven distinct data types, and data types of the same type can be converted automatically to larger data types to accommodate smaller ones. This feature is made possible by implicit type conversion in Java. Conversely, Kotlin doesn’t provide implicit data type conversion, which implies that smaller data types cannot be converted to larger ones.
  3. Data classes in Kotlin versus Java

    Kotlin streamlines the creation of data classes by utilising the ‘data’ keyword for their declaration. Upon doing so, the Kotlin compiler automatically generates the necessary constructor, getter, and setter methods for the class, which saves developers from having to produce them manually.

    Java, on the other hand, requires developers to manually define the constructor, getter, and setter methods for the creation of data classes.
  4. Language scripting in Kotlin vs. Java

    Language scripting automates particular functions that would typically necessitate manual intervention, allowing developers to program more systematically. Although Java does not offer support for language scripting, it can be integrated into Kotlin scripts.
  5. Operator Overloading in Kotlin versus Java

    Operator overloading is a feature of programming languages that enables a single operator to be used with several data types, allowing the same operator to perform various operations depending on the data type it is used with. The + operator, for example, can be used for numerical addition and string concatenation. Unfortunately, Java does not support operator overloading, except for the + operator.

    Kotlin permits developers to use a predetermined set of operator types, including the plus and multiplication symbols, by defining the associated data type’s corresponding member function with an appropriate name to implement operator overloading.
  6. Static members in Kotlin versus Java

    Memory management is achieved in Java using static members. By using the static Java keywords, developers can designate methods, blocks, variables, and nested classes as static members, allowing them to be accessed without instantiating the class.

    Kotlin, on the other hand, does not employ static variables in name fields, unlike other programming languages. Instead, developers need to use the Kotlin object feature to create a companion object within the class, which acts as a static member, granting direct access without interfering with the containing class as it is a stand-alone entity.
  7. String templates and expressions in Kotlin versus Java

    String templates in Java are strings of characters that are shown to the user and consist of string literals enclosed within quotation marks. These templates do not allow for the inclusion of expressions.

    In Kotlin, there are two sorts of string templates: raw strings and escape string templates. These templates allow for expressions to be included in strings, influencing the end result of an existing program.
  8. Smart cast in Kotlin versus Java

    Smart casting is a beneficial feature of the Kotlin programming language that enables developers to manage an object or variable and securely cast it into the corresponding methods and types. This method avoids the need for developers to manually cast objects, saving them time and effort during coding. Furthermore, it helps ensure the accuracy of the code and minimises the possibility of errors occurring.

    Java, on the other hand, lacks smart casting functionality. Therefore, developers must perform two distinct operations, first checking the variable’s type, then casting the object to the desired type.
  9. Type inference in Kotlin versus Java

    Type inference refers to a feature present in certain programming languages that enables the automatic deduction of data types, such as integers, characters, or Booleans, for specified expressions. However, unlike Kotlin, the Java programming language does not provide type inference capabilities. As a result, developers must declare the data type of each variable before using it.

    In contrast, Kotlin supports type inference, removing the need for developers to specify the data type of each variable individually.


Kotlin is a contemporary programming language created primarily for Android development and with Java in mind. Its succinct syntax enables programmers to write more efficient code with fewer lines than Java and other languages. However, for client-side and web app development, many developers still prefer to use Java.

To sum up, when choosing a programming language, developers should carefully consider their project’s needs and take into account the pros and cons of each language to make an informed decision.

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