This repository provides an extensive collection of fundamental and advanced data structures built from the ground up using Java. It serves as a technical showcase of algorithmic problem-solving, focusing heavily on the optimization of both time and space complexities. The implementations cover essential architectures ranging from linked lists and hash maps to complex trees, graphs, and sorting algorithms. By engineering these structures natively, the collection demonstrates a profound understanding of object-oriented design, memory allocation, and computational efficiency. It reflects a commitment to the core computer science principles that are essential for architecting high-performance, scalable enterprise backend systems.