So, you can only use a switch to perform an action when one specific variable has a certain precise value. We can explicitly declare the type of a variable like so: / val foo: Int 7. However it cannot replace all sort of if/else sequences but just those which compare a value with some constant. Since Kotlin 1.3 the main function can also be defined without any.

One of the most useful improvement, especially if you come from Java, is the when construct.Ī traditional switch is basically just a statement that can substitute a series of simple if/else that make basic checks. Kotlin is full of these pragmatic improvements, getting its user a language that just feel good to use. There are a few differences, but we’ll leave them for a later chapter.There are two kinds of innovation: new perspectives that changes how we look at things and pragmatic improvements that changes how we do things. As you can see, the syntax for generics is very similar to Java. The function is generic: it works on collections that contain elements of any type.

The function just appends the elements of the collection to a StringBuilder, with a separator between them and surrounded by prefix and postfix. Hello, If I understand your question right, Kotlin supports the use of generic types in suspend functions just like in regular functions. Functions always return a value, Functions that dont actually return anything in kotlin will return Unit, a type that has a single value, also called Unit. Let’s introduce the function joinToString without using any of Kotlin’s new features in this area, and then rewrite it in a more idiomatic style. Imagine we need the elements to be separated by semicolon and surrounded by round brackets instead of the default square ones: > println(joinToString(list, ' ', '(', ')')) (1 2 3) > val list = arrayListOf(1, 2, 3) > println(list) ❶ The Kotlin standard library is no exception. Almost every project has its own StringUtil class with a bunch of functions including joinToString.

Java collections have a default toString implementation, but its output is fixed and it’s not always what you need. In this article, excerpted from Kotlin in Action,

Any type in kotlin