You can differentiate collections based on a few questions: Most are implemented as interfaces, with concrete implementations varying between each Kotlin collection type. Note: You can open Collections.kt from the Kotlin standard library and take a look at all the Kotlin collections definitions. Many programming languages provide different types of collections so you can use them in different scenarios. In common terms, this is a collection because you can collect those objects and add or remove them when needed.īut collections aren’t only for storing data. In this case, you have to use a group of objects of the same type. In addition to creating your own types, you often need to work with a large number of objects which are of the same type.įor example, if you’re writing an e-reader application, you’ll display and manage many books. Those available in most languages are Boolean, Int, Char, String and Object/Any types, along with several different number types.īut you won’t always work with only those types. This is true in Kotlin as well.įurthermore, types in object-oriented programming languages are often divided into primitive and object types. If you’ve got some experience with programming, you should know there’s a small number of data types in every programming language. And on the right-hand side, you have buttons to run the code, change the version of Kotlin and share the code.īut that’s enough talk about the projects, time to start learning! What are Collections?

On the left-hand side, you have the code editor, in which you’ll add all the snippets of code.

Any kotlin example