This project is a practical tutorial demonstrating how to build enterprise-grade AI applications using LangChain4j with Java. It implements an AI coding assistant that serves as a programming mentor and job interview coach, covering core AI development patterns including LLM integration, conversation memory, structured output, RAG retrieval augmentation, tool calling via function hooks, MCP protocol support, vector database usage, and streaming responses. The backend is built with Spring Boot and Vue.js frontend, with observability and safety guardrails included.