KIP-1369 — API-Contract Annotations for Nullity/Thread Safety

Discussion Client

Annotates Kafka's public API with CLASS-retained SpotBugs and JSR-305 contract annotations — `@Nullable`/`@NonNull` for null-safety and `@GuardedBy`/`@Immutable`/`@ThreadSafe`/`@NotThreadSafe` for concurrency — added `compileOnly` so nothing lands in shipped runtime dependencies. These contracts currently exist only in Javadoc prose, so a method that starts returning null or a field read without its lock compiles clean and fails at runtime, and SpotBugs already in the check phase can enforce the annotated form with no new setup.

Details