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# Data structures

* Most languages provide two types of containers:
  * Sequential containers store objects at a particular position, denoted by a numerical index.
  * Associative containers use the object itself to determine where the object should be stored inside the collection.
* For certain contianer methods to work, the objects must have implement some form comparability and equivalence (equals() and hashcode())
* The object is not store in the container, it is the reference to the object
* The Collections API defines a set of interfaces specifying the operations a container of that type must conform to
* Mutable collections which allow mutation of their state in place
  * he majority of standard collections from java.util.
  * When you add or remove elements there, you get the changes at all places which keep a reference to the collection instance.
* Persistent collections are the collections, which persist their previous state when mutation operation is applied on them.
  * When you apply mutation operation on such collection, you get a new independent instance of it, with updated content.
  * Such characteristic makes them effectively immutable.
  * There are plenty different implementations of persistent collections in Java ecosystem.
  * External libraries such as Vavr
* What is it?
  * <https://en.wikipedia.org/wiki/Data_structure>
  * <https://www.geeksforgeeks.org/data-structures/>
  * <https://medium.com/swlh/introduction-to-data-structures-9134b7d064a6>
  * <https://www.youtube.com/watch?v=DuDz6B4cqVc>
  * <https://medium.freecodecamp.org/10-common-data-structures-explained-with-videos-exercises-aaff6c06fb2b>

## Contents

* Arrays
* List/ArraysList
* Map/HashMap

## Links

* [https://dzone.com/articles/java-collections-part-1?utm\_medium=feed\&utm\_source=feedpress.me\&utm\_campaign=Feed: dzone%2Fjava](https://dzone.com/articles/java-collections-part-1?utm_medium=feed\&utm_source=feedpress.me\&utm_campaign=Feed:%20dzone%2Fjava)