The Java Collection Framework Hierarchy

Iterable

• The root interface of the collection hierarchy.
• Provides the iterator() method to iterate over the elements of a collection.

Collection

• Represents a general-purpose collection.
• Provides methods for adding, removing, searching, and iterating over elements.

Set

• Represents a collection that does not allow duplicate elements.
• Has three implementations: HashSet, LinkedHashSet, and TreeSet.

List

• Represents a collection that allows duplicate elements and maintains the order of elements.
• Has three implementations: ArrayList, LinkedList, and Vector.

Queue

• Represents a collection that follows the FIFO (First-In-First-Out) order.
• Has two implementations: ArrayDeque and LinkedList.

Deque

• Represents a double-ended queue (deque) that allows elements to be added or removed from both ends.
• Has one implementation: ArrayDeque.

Map

• Represents a collection of key-value pairs.
• Does not extend Collection.
• Has three implementations: HashMap, LinkedHashMap, and TreeMap.

References: How to Learn Java Collections – A Complete Guide