Learning Kotlin – Part 1


I wanted to try writing an Android app. In spite of using plain old Java I wanted to give the new kid on the block Kotlin (from the Jetbrains folks) a try.

First observations

Coming from a Python background it’s good to see that Kotlin doesn’t use semi-colons! But the curly braces from Java make code blocks are still there, hmpf…


Kotlin has two ways of declaring “variables”:

  • var: think variable: this is a mutable
  • val: think values: this is read-only like const

Data Types and Type Inference

A nice thing about Kotlin is type inference. When it is clear which data type is meant you can leave out the data type from the declaration


val firstName = "Tony"
val lastName  = "Stark"


You can concatenate strings with the plus operator as you can do it in Python

val fullName: String = firstName + " " + lastName

Print and String interpolation

Kotlin has a built-in println function so you can stop typing System.out.println()

Less visual noise!


A neat little feature is the string interpolation syntax. If You want to concatenate strings for logging output, you can write $stringName Locks similar to the Python f-Strings

println("Name: $fullName")

But there is more to it:
You can for example call functions inside strings as well:

println("String length: ${fullName.length}")

or access indices

println("2nd Index: ${fullName[2]}")

Stay tuned for the next part!