Hands-On Design Patterns with Kotlin

Join family

In the previous example, we used the side effect of printing to the console, which is not favorable in terms of functional programming. What's more, we also have this ugly comma at the end of our output as follows:

0:1, 1:4, 2:9, 3:16, 4:25,

There must be a better way.

How many times have you had to actually write code to simply concatenate some list of values into a string? Well, Kotlin has a function for that:

    val numbers = (1..5)    println(numbers.joinToString { "$it"})

The preceding code will give the following output:

1, 2, 3, 4, 5

Simply beautiful, isn't it?

And if you want to separate it with other characters, or don't want spaces, there's a way to configure it:

println(numbers.joinToString(separator = "#") { "$it"})