java-solid-designlisted

# Skill: java-solid-design ## Activation Contract Use this skill when asked to evaluate or improve Java object-oriented design using SOLID, cohesion, coupling, composition, inheritance, interfaces, and dependency direction. Do **not** use this skill for simple naming/style cleanup, pattern shopping, framework wiring only, or non-Java code. ## Responsibility This skill teaches Java SOLID design review. It does not call other skills, prescribe interfaces everywhere, or force pattern usage. ## Required Context - Classes/interfaces involved. - Change scenario or pain point. - Public API compatibility constraints. - Existing dependency direction and lifecycle ownership. ## Context Budget - Keep this `SKILL.md` executable. - Use `references/solid-java.md` for principle-specific guidance. ## Hard Rules - Do not apply SOLID mechanically; connect every recommendation to a real change pressure. - Prefer composition over inheritance unless subtype substitution is genuinely valid. - Introduce interfaces for stable contracts or test/design seams, not ceremony. - Protect LSP: subclasses must honor superclass/interface contracts. - Keep dependencies pointing toward stable policy, not volatile details. - Avoid splitting responsibilities so far that workflow becomes harder to understand. ## Decision Gates | Condition | Action | |---|---| | Class has multiple reasons to change | Propose responsibility split around change axes. | | Conditional selects behavior by type | Consider po