Basic Kotlin syntax

Kotlin syntax will look familiar to developers with experience of other languages based on C style syntax, such as C, Java, Scala, Groovy, and TypeScript.

General features

Various Kotlin features are common among other JVM Languages. If you have experience of Java, you'll feel at home with Kotlin.

Packages

Packages are sets of files (usually defined in the same directory) that define logic units, for example, controllers, and repositories.

To set a file in a particular package, use the package keyword in the first line:

package com.packt.functionalkotlin

Ideally, a file inside the package com.packt.functionalkotlin should be in the directory com/packt/functionalkotlin. It makes files easier to find but isn't mandatory in Kotlin.

String concatenation and interpolation

String concatenation in Kotlin uses the plus (+) operator:

val temperature = 12

println("Current temperature: " + temperature + " Celsius degrees")

String interpolation is an easy way to do complex concatenations:

val...