Java Data Structures: The Very Simple Book

A from-scratch Java and data structures book built around dry-running code by hand rather than memorising it. Starts at the ground floor — every keyword, every operator, decisions and loops, methods and the call stack, recursion, arrays and strings — before building objects and reasoning about cost (Big-O, brute force vs. optimised). The core of the book hand-builds every major structure from nothing (linked list, stack, queue, hash table, trees, heap/priority queue, graphs, trie), then covers the Java Collections Framework you'd actually use day to day. Closes with 100 worked programs across numbers, arrays, strings, and structures, plus a chapter on the mistakes that cost the most hours and how to dry-run properly.