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Since Android apps appeared in the Play Store, Java has become a symbol and main language for Android app development. At Google I/O 2017, Google acknowledged Kotlin as the official language for Android development, and the tough opposition has begun.

Today, the languages are frequently compared and a lot of experts predict young and developers-friendly Kotlin to take the place of old and mature Java. Is it true? As a custom software development company, we couldn't miss an opportunity to compare these two technologies.  Let’s find out.

What is Java?

Java is a programming language developed by James Gosling and released in 1995 by SunMicrosystems. The language is considered to have a shallow learning curve, advanced security features, and a high degree of platform independence gratefully to the Java Virtual Machine feature.

Every single year Java is predicted to disappear from the list of best languages for web development and every year it remains in the charts. For 20 years, Java maintained the position of the most popular programming language, according to the TIOBE index, being shifted to the third position, as of February 2022 and taking second place, according to the PYPL Index.

Java is updated every 6 months regardless of disasters and pandemics, which undoubtedly strengthens its image of a stable and trusted language.

Benefits of Java

  1. Java is an object-oriented programming language. It allows programmers to design modular programs and reusable code;
  2. Java runs on JVM that is very beneficial in terms of memory management, code optimization, garbage collection, and other developer-friendly features;
  3. It has an easy learning curve compared to most other programming languages;
  4. Platform independence enables one to move flawlessly from one computer system to another.
  5. Java is a secure language that uses a Security manager for each application, allowing developers to define the access rules for classes. It also reduces security risks by avoiding the use of explicit pointers;
  6. Java programs are relatively inexpensive to develop and maintain as they are dependent on a specific hardware infrastructure to run;
  7. Strong memory management makes Java a robust programming language.

Challenges of Java

  1. Java is memory-consuming and therefore much slower compared to native languages such as C or C++. JVM requires an extra level of compilation and abstraction resulting in slower performance;
  2. It provides not very attractive look and feels of GUI despite the existence of many popular frameworks;
  3. Working mainly on storage, Java doesn’t focus on the backup of data which is considered to be one of its biggest disadvantages and reasons for losing popularity.
Best Applications Developed Using Java

What is Kotlin?

Kotlin is a general-purpose programming language, designed to interoperate fully with Java. The creators of Kotlin tried to take the best features from JavaScript, TypeScript, Java, C#Rust, and many other languages to build the language that would compile as fast as Java but would be better in all other features.

In 2019, Google made the announcement that Kotlin became its preferred language for Android application developers. Though, compared to Java, Kotlin is still much less popular, taking 28th position in TIOBE Index and 12th, according to PYPL Index.

Benefits of Kotlin

  1. Kotlin is fully compatible with Java. You can add all Java tools and frameworks to your Kotlin projects;
  2. Data classes, type interface, properties. and smart casts make Kotlin code very concise, therefore, easy to read, maintain, and apply changes;
  3. Kotlin code allows fewer errors and prevents common programming mistakes;
  4. Kotlin eliminates null references which is one of the major drawbacks of Java;
  5. Bugs are detected at compile-time, allowing developers to fix errors before runtime which makes Kotlin a stable and consistent language;
  6. It’s a very dynamic and clear language that allows developers to write and deploy the code very fast.

Challenges of Kotlin

  1. In a variety of cases Kotlin is faster than Java though Java still stays incomparable in the matter of clean building;
  2. Minimal tools for programming language learning.

Best Applications Developed Using Kotlin

Kotlin vs Java — Let’s Look at the

  1. Null Safety

Null-safety is considered to be the best feature of Kotlin that gives it a priority in Kotlin vs Java opposition. In 1965, Tony Hoare, presented the infamous null reference upon the world, calling it later “a billion-dollar mistake” because of its numerous problems caused by this design flaw. The idea behind this is to let users attribute a null value to any variable. Kolin uses a type system that differentiates between nullable and non-nullable references, this way, solving the problem.

2. Data Classes

Kotlin introduces the concept of data classes that are used as simple data containers and don’t confine any additional logic. In other words, they enable developers to avoid writing boilerplate code. This feature allows writing much easier and cleaner code compared to Java.

3. Extension Functions

To extend the functionality of an existing class in Java, a programmer has to create a new class and inherit the functions from the parent class. In simple words, the extension function is not available. In contrast to Java, Kotlin gives developers an opportunity to extend the functionality of classes without the necessity to inherit from a class. They just need to prefix the name of the class that needs to be extended to the name of the function created by using the ‘.’ notation.

4. Smart Casts

If one needs to cast an object in Java, they must check the variables type in line with the operation. While Kotlin handles casting checks by the smart compiler that can automatically manage redundant casts through the “is-checks” keyword.

5. Functional Programming

Kotlin has both object-oriented and functional constructs while Java is more suitable for object-oriented programming. Though things have changed with Java 8, Java is still not suitable for starting a program from scratch in functional programming. Whereas Kotlin has the best support for collection processing, quicksort, powerset, and more.

6. Concurrency vs Coroutines

Coroutines present so-called “lightweight threads” that enable developers to write asynchronous non-blocking code. The biggest advantage of coroutines is that they are not bound to a single code. With Kotlin coroutines, programmers can write parallel code in a sequential way without the inconveniences caused by contextual overheads typical for Java threads. Java maps these threads to the kernel level thread through system calls that are easier to program with. The alternative is to use user-level threads. Java Loom is actively solving this inconvenience, supporting high-throughput lightweight concurrency and new programming models on the Java platform.

Kotlin vs Java — Popularity and Adoption

Java was comfortably sitting at the top of the most popular programming languages for almost twenty years until the end of 2021. Today, Java has been shifted to the third position, according to the TIOBE Index, giving its place to Python and C. Kotlin takes 28th position in the rating. TIOBE Index is based on the number of skilled programmers worldwide, courses, and third-party vendors. You can also check the definition here.

According to the PYPL Index, which analyzes how often language tutorials are searched on Google, Java is also much higher than Kotlin — second and twelfth position correspondingly.

According to Stackoverflow developer survey 2021, Kotlin is much more loved by developers compared to Java. What is more, a lot of engineers who opt for Kotlin, are ex Java developers.

Most Loved Programming Languages

The chart below shows how the development community is interested in learning and using the languages. Both languages are in the top 10 though Java is behind Kotlin by 1,7%.

Most Wanted Programming Languages

Kotlin vs Java — Which One Is Easier to Learn

The answer heavily depends on your level of experience with programming. If it’s your first programming language, all languages are relatively tough. Comparing Kotlin vs Java for beginners, Java has a lot of well-established resources for learning syntax and basics of programming while resources for learning Kotlin are scarce.

Kotlin is easy if you know Java, otherwise, it’s not.

Kotlin vs Java — So Which One Is Better

Old simple Java has a number of flaws. Though besides some limitations, it still remains one of the most popular programming languages because of its security, platform independence, and maintainability features. On the other hand, Kotlin is gaining huge popularity and is definitely well worth picking up at the moment, especially, if you already know Java, it won’t be difficult. From the point of view of the development process, Kotlin helps to remove boilerplate code and keep everything clean and short. The development community and Google community also show support for Kotlin so we can predict it to increase its popularity in the near future.

Kotlin vs Java


In our opinion, Java isn’t going to disappear in the near future. It will remain a preferred choice for backend development while Kotlin will beat Java in Android development (or has already beaten).

We hope this comparison will help you understand the difference between languages and assist you in making the choice of which language to learn or choose for your project.

In case you have any questions, get in touch with us through our contact form and our experts will choose the best programming language depending on your product requirements.

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