Java Best Practices

This is a comprehensive reference guide for writing maintainable Java code, covering SOLID principles, Clean Code practices, and modern Java features like Optional, streams, and lambdas. Use it during code reviews or when refactoring legacy code that's gotten messy. The examples are practical, showing both bad and good implementations side by side for things like Single Responsibility and Open/Closed principles. It also covers Spring Framework patterns, JUnit 5 testing, Mockito mocking, and common anti-patterns to avoid. The skill assumes you know Java 8+ and OOP basics. It's designed to be referenced by code review agents but works just as well as a checklist when you're questioning whether your class is doing too much or if there's a cleaner way to handle that growing if-else chain.