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?

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