Class, interface, or method should not be extended

Reports classes, interfaces and methods that extend, implement, or override API elements marked with @ApiStatus.NonExtendable.

The @ApiStatus.NonExtendable annotation indicates that the class, interface, or method must not be extended, implemented, or overridden. Since casting such interfaces and classes to the internal library implementation is rather common, if a client provides a different implementation, you will get ClassCastException. Adding new abstract methods to such classes and interfaces will break the compatibility with the client's implementations.