Common

Class implements Publisher  

Reports classes that directly implement the Publisher interface.

Class implements Subscriber  

Reports classes that directly implement the Subscriber interface.

Return null or something nullable from a lambda in transformation method  

Reports transform operations that may return null inside a Reactive Stream chain.

Throw statement in Reactive operator  

Reports throw expressions in the Reactor/RxJava operator code.

Too long same methods chain  

Reports long Reactive Streams transformation chains.

Unused publisher  

Reports unused Publisher instances.