(The in-depth study of Java design patterns is aimed at readers with certain Java language foundation and programming experience, aiming to cultivate readers' good design pattern thinking methods and strengthen their understanding of object-oriented thinking. In depth Research on Java Design Patterns is divided into 12 chapters. It first emphasizes the importance of interfaces and abstract classes in design patterns, and introduces the use of reflection technology in design patterns. Then, 10 of the 23 commonly used design patterns are selected for specific explanation, including 2 creation patterns, 4 behavior patterns, and 4 structural patterns. In depth Research on Java Design Patterns provides thorough theoretical explanations and in-depth examples. The explanation of design pattern leads to the topic to be discussed from the analysis of a common thing in life, and then analyzes the design pattern in depth, and finally explores its use. All the examples in the use exploration part originate from the use project. The content touches on Java, JSP, JavaScript, Ajax and other practical technologies, covering a wide range of knowledge. The In depth Study of Java Design Patterns can be used by undergraduate and graduate students of computer related majors in colleges and universities for design patterns, software system architecture and other courses, and also has certain reference value for high-end programmers, software engineers, system architects and other professional researchers.)