ArrayList Internals
Dynamic array implementation and growth strategy.
Linked List
Singly and doubly linked list operations.
Stack
LIFO structure — push, pop, peek.
Queue
FIFO structure and circular queue.
Deque
Double-ended queue with ArrayDeque.
HashMap Internals
Buckets, hashing, and treeification.
HashSet
Unique element collection backed by HashMap.
TreeMap
Red-black tree sorted map.
TreeSet
Sorted unique elements.
Priority Queue
Heap-based priority queue.
Binary Tree
Tree traversal and basic operations.
Binary Search Tree
Ordered tree with search, insert, delete.
AVL Tree
Self-balancing BST with height balance.
Red-Black Tree
Balanced tree used in TreeMap and TreeSet.
Trie
Prefix tree for string storage and lookup.
Segment Tree
Range query and update structure.
Fenwick Tree
Binary indexed tree for prefix sums.
Union-Find
Disjoint set union with path compression.
LRU Cache
Least recently used cache implementation.