Let's Learn About Kotlin

They say it's better than Java?

What is Kotlin

Kotlin is a language created by Jetbrains, the company famous for Intellij. Kotlin's catchphrase is Concise. Cross‑platform. Fun, which can be interpreted as a concise language that supports multiple platforms.

Does it support multiple platforms?

Looking at Kotlin's official overview, Kotlin Multiplatform is introduced first. kmp

Among these, I found it unfamiliar that it's used in web development, so I looked into it. In fritz2, one of the Kotlin/JS frameworks, web code is written like this:

// fritz2
fun main() {
    render {
        div("my-style-class") {
            h2 {
                +"Hello Peter!"
            }
        }
    }
}

(I'll use JS.)

Getting back to the main point, through Kotlin Multiplatform, I learned that you can achieve multiple platform services with one language. The platforms that seem to be most used in actual projects are Android/iOS and Server (Spring).

Is it concise?

As I'll introduce later, since Kotlin is ultimately converted to bytecode and executed by the JVM, it's often compared to Java code.

// java
function main() {
    String name = "stranger";
    System.out.println("Hi, " + name + "!");
    System.out.print("Current count:");
    for (int i=0; i<=10; i++) {
        System.out.print(" " + Integer.toString(i));
    }
}
// kotlin
fun main() {
    val name = "stranger"
    println("Hi, $name!")
    print("Current count:")
    for (i in 0..10) {
        print(" $i")
    }
}

You can see the conciseness compared to Java standard libraries that started with package names like System.out.

Kotlin's Build Process

kmp JVM is a virtual machine for executing *.class (bytecode). Java is converted to *.class files by the Java Compiler.

Kotlin also uses JVM. Like Java, it's converted to *.class by the Kotlin Compiler. This *.class is loaded by JVM's class loader along with kotlin runtime, then converted to native code suitable for each operating system, and finally the program is executed.

Side Notes

  1. In the next post, let's install and use the Kotlin Compiler.
  2. Kotlin's native pronunciation is said to be 'Kotlin'.
Kotlin