141 Java Refactoring With Modern Features

This is a systematic refactoring guide that modernizes legacy Java codebases by replacing old patterns with Java 8+ features like lambdas, streams, Optional, and the java.time API. It even covers newer additions like Java 25's flexible constructor bodies and module imports. What I appreciate here is the mandatory compile-before-refactor safety check, which prevents you from breaking a codebase that was already broken. The skill works through a reference document with good/bad code examples for each pattern, so you're not just blindly applying transformations. It's built for incremental, behavior-preserving changes with full verification afterward. If you're maintaining Java code that still uses anonymous classes and Iterator loops everywhere, this gives you a structured way to chip away at the technical debt without introducing regressions.