Modern Java

Apply these rules when writing or reviewing Java code.

Match the project's configured Java release, compiler flags, libraries, and style. Use newer language or library features only when that release supports them and they improve clarity.
Prefer clear, immutable value types. Use records for transparent data carriers and sealed types when a closed set of variants is part of the domain; do not force these forms onto mutable entities or framework-bound types.
Use pattern matching, switch expressions, and text blocks where supported and clearer than older forms. Keep control flow explicit; streams are not automatically clearer or faster than loops.
Prefer local var only when the initializer makes the type obvious. Keep public APIs explicitly typed and avoid raw types and unchecked casts.
Keep classes and methods focused, use descriptive names, and make state and side effects easy to see. Prefer composition and small interfaces at real boundaries over speculative abstractions.
Use try-with-resources for AutoCloseable resources. Preserve interruption, exception causes, and precise failure context; do not swallow exceptions or use exceptions for ordinary control flow.
Define nullability and mutability expectations at API boundaries. Prefer standard collection and Optional conventions without using Optional for fields or parameters by default.
Avoid deprecated APIs and obsolete date/time or concurrency utilities when supported standard replacements fit the target release. Remove dead code and unused dependencies.