RxJava a long time do not write code, the compiler today before writing a demo project, suddenly being given.
Can not find the class file org.reactivestreams.Publisher
Do not know why org.reactivestreams gone, found a bit solutions, the need to introduce reactive-streams.jar jar package.
Find the next, of course, is the best solution
implementation "org.reactivestreams:reactive-streams:1.0.2"
In this way it is introduced.