Tell about the hierarchy of collections in Java.

In Java, the collection hierarchy is built around the Collection interface, which is extended by several key interfaces:

• Collection — the base interface for all collections except Map.
  • List — an ordered collection that allows duplicates (e.g., ArrayList, LinkedList).
  • Set — a collection without duplicates (e.g., HashSet, TreeSet).
  • Queue — a collection for storing elements in processing order (e.g., LinkedList, PriorityQueue).

Separately, there is the Map interface, which does not inherit from Collection, but is part of Java collections. It stores key-value pairs (e.g., HashMap, TreeMap).

Example hierarchy:

java.lang.Object
  └── java.util.Collection
        ├── List
        ├── Set
        └── Queue

java.util.Map (separately)

Each of these collections has its own features regarding storage, access, and performance.