The keys in a map are unique, which means we cannot have two pairs with the same key in a map. MutableSet: a Set that supports adding and removing elements.Set: an unordered collection of elements that doesn’t support duplicate elements.MutableList: a List that supports adding and removing elements.

As it’s ordered, we can request an item by its position, using the get function. It represents a generic ordered collection of elements.

List: Probably the most used collection.

It provides extra functions such as add, remove or clear among others.

MutableCollection: a Collection that supports adding and removing elements.

All the methods for this kind of collections are only to request data, because collections are immutable. We get access to functions that return the size of the collection, whether the collection is empty, contains an item or a set of items.

Collection: This class represents a generic collection of elements.

MutableIterable: Iterables that support removing items during iteration.

Any classes that inherit from this interface represent a sequence of elements we can iterate over. CollectionsĪlthough we can just use Java collections, Kotlin provides a good set of native interfaces you will want to use: Today I’ll be talking about the different types of collections Kotlin provides, as well as the available operations over them.

This article is not Android specific, but it will boost Android Apps development in many different ways. Kotlin provides an awesome set of operations that wouldn’t be possible (or really verbose) when using a language which doesn’t support lambdas. In the end, lambdas are the basis to implement lots of functional features, such as the ones we are talking today: Collection operations. We talked about them in the (Unleash functional power on Android (I): Kotlin lambdas). Lambdas are a great powerful tool to simplify code, but also to do things that were not possible before.

Foreach kotlin index