Java Data Structures — Complete Course
A phase-by-phase Java 17+ data structures course spanning 16 structures from foundation to advanced — Big O notation and the stack/heap memory model, generics, then arrays, strings, ArrayList, Stack, Queue and Deque, then HashMap, LinkedList, Binary Tree, BST and Heap, and finally AVL Tree, Trie, Graph BFS/DFS, Segment Tree and Union-Find. Every topic works through concept, visual, complexity, Java code, dry run, edge cases, and practice.
Sixteen structures is a real commitment, so here's the honest read: the first half, arrays through HashMap, is where most interview questions actually live, and the second half — AVL, Trie, Segment Tree, Union-Find — is where the differentiating questions live for senior roles. Prepping for a mid-level role, you can stop after Heap and still be well covered. Every topic dry-runs the code, which is the part that actually builds intuition — reading code and tracing code by hand are different skills.