Think Data Structures: Algorithms and Information Retrieval in Java. A. B. Downey

 This book is intended for college students in computer science and related fields, as well as professional software engineers, people training in software engineering, and people preparing for technical interviews. Before you start this book, you should know Java pretty well; in particular, you should know how to define a new class that extends an existing class or implements an interface. If your Java is rusty, here are two books you might start with: