Kotlin Programming Cookbook

How to do it…

Now, let's follow these steps to understand how Generics works in Kotlin, with the help of some examples:

1. Let's start with a generic class that we can instantiate using any type of parameter:

fun main(args: Array<String>) {    val intgen: GenCl<Int> = GenCl<Int>(10)    println(intgen.a)    // We are letting Kotlin compiler infer type    val strgen = GenCl("A string")    println(strgen.a)}class GenCl<T>(t: T) {    var a = t}

The output of this program is this:

10A string

2. We can also restrict what types are allowed in our generic class like this:

fun main(args: Array<String>) {    val intgen: GenCl<Int> = GenCl<Int>(10)    println(intgen.a)    val flgen = GenCl(1.0)    println(flgen.a)}// Restricting T to only be of type Numberclass GenCl<T: Number>(t: ...