# What is Kotlin and Why use it?

### What is Kotlin?

* `Kotlin` is a development language created by `JetBrains`, renowned for developing the world's leading commercial development tool, **IntelliJ IDEA**. It can be said that it was newly created by a group of experts with a deep understanding of the **Java** language to maintain enterprise-level applications with minimal effort. It was first introduced in 2011, went through a beta period, and **1.0** was released in 2016. As of 2024, **1.9.23** has been released. (Interestingly, **JetBrains** consists of Russian and Czech developers, and **Kotlin** is named after an island in Russia.)
    

### The Future of Kotlin is Bright.

* **Kotlin** was initially created by **JetBrains**, who actively lead its version upgrades. The fact that one of the world’s leading development tool manufacturers, spanning the **Java**, **Python**, and **PHP** communities, is behind this language suggests that it has a low chance of failing in the future.
    
* More interestingly, in 2017, Google adopted **Kotlin** as the official language for Android. As of two years later, all reference documents issued by Google prioritize **Kotlin**. (Moreover, the official development tool for Android, `Android Studio`, was created by **JetBrains**.)
    

### Kotlin is More Concise than Java.

* One of the biggest shocks for someone coming from a scripting language to **Java** is its verbosity. For the simple purpose of holding data, one must repeatedly implement **Getter**, **Setter**, **Equals**, **HashCode**, **ToString**, etc., manually. Although this can be solved by using an external library like **Lombok**, it’s hard to escape the outdated and unproductive feeling inherent to the **Java** language. **Kotlin** neatly solves these issues at the language level with its **data** class. This is why once Java developers start using **Kotlin**, they can never go back.
    
* **Kotlin** is one of the most advanced languages, resulting from the long deliberation of **Java**'s top experts. Its concise design philosophy can be found throughout its basic syntax and libraries. Another charm of **Kotlin**’s conciseness is that it doesn't sacrifice the readability of the source code for brevity. Unless intentionally written in a complicated manner, there are hardly any cases where code reading is difficult.
    

### Kotlin is Easy to Learn.

* Explaining the code of an operating **Java** application to someone who is learning **Java** for the first time is not an easy task. **Kotlin** has eliminated verbosity at the language level. That is, it has minimized the parts of the basic syntax to memorize and reduced the source code needed for implementing logic, making it an entirely unburdening language for beginners. (According to a statistic, it took **Java** developers an hour to understand **Kotlin** source code, and they were fully adapted in three days.)
    

### Kotlin is Friendly to Type-Safety.

* **Type-Safe** means explicitly enforcing the specific type of a variable that has meaning from a data perspective at the source code level. For example, a variable holding a member's gender cannot contain any value other than **MALE** or **FEMALE**, and it ensures that this value does not change to a completely different type.
    
* The reason **Java** has been the throne in the backend worldwide for so long is precisely because it encourages and aims for **Type-Safe** at the language level. Enterprise applications designed with **Type-Safe** in mind discover errors in the development compile stage. If designed only considering immediate productivity without regard for **Type-Safe**, errors are unexpectedly found after deployment under specific circumstances. While this may be acceptable for simple applications that can be quickly fixed and redeployed, it is not tolerated in crucial services handling money. This is why the most conservative financial sector insists on **Java**. (Meanwhile, **JavaScript** and its basis **Node.js**, along with **Python**, are dynamic typed languages that are completely opposite. The frontend sector, due to the high degree of freedom and dynamic typing characteristics of the **JavaScript** language, leading to an unbearable number of errors in enterprise-level applications with large teams, prompted **Microsoft** to introduce and popularize **TypeScript** to strongly control **Type-Safe**.)
    
* However, there are not only advantages. Due to these characteristics, **Java** has the disadvantage of verbosity and unproductivity compared to other languages. But, with the emergence of **Kotlin**, it maintained the strengths of **Type-Safe** while also possessing conciseness and productivity as advantages. Moreover, **Kotlin** supports **Null** checks for variables, which is not available in **Java**. Therefore, **Kotlin** can be said to be very friendly to **Type-Safe**. (In fact, serious efforts are underway to solve **HTML**, **CSS** syntax through **Kotlin**'s **DSL** to increase reusability and block errors at their source.)
    

### Kotlin and Java are Interoperable.

* Even if you recognize the advantages of **Kotlin**, the sigh that comes out at the thought of changing all the existing **Java**\-developed legacy services to **Kotlin**. Is there no way? In fact, as mentioned earlier, since **Java** and **Kotlin** are siblings sharing the same **JVM** ecosystem, it is entirely possible to freely mix **Kotlin** in projects developed with **Java**. It is also feasible to write new features in **Kotlin** or to use existing developed classes in **Kotlin**. Whether to implement new features only or to change the entire thing is entirely up to the developer.
    
* For methods to mix the two languages in a **Spring Boot**\-based project, refer to [this article](https://jsonobject.hashnode.dev/how-to-add-kotlin-feature-to-java-spring-boot-project) on this blog.
    

### Kotlin Can Use Java's Libraries and Frameworks.

* **Java** is a very mature language, first released in 1995. Since then, countless talented developers around the world have freely shared a wealth of libraries and frameworks, arguably more so than any other language. As mentioned earlier, since **Kotlin** can be mixed with **Java**, libraries and frameworks can also be used as is. In fact, combining **Kotlin** with **Java**'s celebrated technologies such as **JPA**, **Hibernate**, **Spring Boot Data JPA**, and **Querydsl** can be quite productive.
    

### Kotlin and Java Perform Equally.

* When source code written in **Java** or **Kotlin** is compiled, it is converted into byte code with a **.class** extension that can be executed in real operational environments, meaning that the final output of both languages is essentially the same. (It's obvious that performance cannot be discussed when the output is identical.) Therefore, the byte code can be executed as is in any operational environment where the **JVM** is installed. This is also why mixing **Java** and **Kotlin** languages within a project, and why you can use Java source code and libraries in Kotlin source code without any problems.
    

### Kotlin is Within the JVM Ecosystem.

* The entity that executes the compiled results of source code written in **Java** or **Kotlin** is called the **JVM** (**Java Virtual Machine**). The development of the **JVM** involves various global **IT** companies under the ownership of Oracle. As for free **JVM**s, `Azul Zulu` from the US is a leading example, and **Amazon** has also released `Amazon Corretto`, a **JVM** optimized for their **EC2** instances.
    
* Developing in **Kotlin** means being able to operate services under the high-performance **JVM** environment of this globally powerful ecosystem.
    

### Recommended Learning Resources

* [Kotlin Compact](https://kotlincompact.com/)
    
* [From Java To Kotlin](https://github.com/amitshekhariitbhu/from-java-to-kotlin)
    
* [Java to Kotlin: A Refactoring Guidebook](https://java-to-kotlin.dev/)
    
* [Kotlin is like TypeScript](https://gi-no.github.io/kotlin-is-like-typescript/)
    
* [JetBrains - Learn Kotlin by Example](https://play.kotlinlang.org/byExample/01_introduction/01_Hello%20world)
    
* [Dave Leeds on Kotlin](https://typealias.com/)
    
* [YouTube - Philipp Lackner](https://www.youtube.com/@PhilippLackner)
    
* [YouTube - Duncan McGregor](https://www.youtube.com/@RefactoringDuncan)
    

### Further Reading

* [Why Kotlin?](https://blog.danlew.net/2017/05/17/why-kotlin/)
    
* [Why you should totally switch to Kotlin](https://medium.com/@magnus.chatt/why-you-should-totally-switch-to-kotlin-c7bbde9e10d5)
    
* [Why Should You Use Kotlin for Backend Development?](https://www.turing.com/blog/why-use-kotlin-backend-development/)
    
* [Quora - Kotlin users: Have you found Kotlin to be better than Java?](https://www.quora.com/Kotlin-users-Have-you-found-Kotlin-to-be-better-than-Java)
    
* [Quora - Have you found Kotlin to be better than Java?](https://www.quora.com/Kotlin-users-Have-you-found-Kotlin-to-be-better-than-Java)
    
* [Adding Kotlin to Java + Spring Boot Project](https://jsonobject.hashnode.dev/adding-kotlin-to-java-spring-boot-project)