Refactor and modernize Java code idiomatically

Apply version-gated Java refactorings

When code quality needs improvement and you want safe, language-version-aware refactorings (lambdas, streams, records, pattern matching) applied.

• · Java code (method, class, or block)
• · Target Java version (optional)

• · Before/after refactoring snippets
• · Minimum Java version for each change
• · Offer to apply changes

Java code provided; build config or target version known

• · Java version not detected → asks user to specify target