Cannot resolve method subscribe()

[theGeekyLad]

Issue

After initialising mStompClient, calling subscribe() on mStompClient.topic() errors out at compile saying:

Cannot resolve method 'subscribe(<lambda expression>)'

What could be the issue?

Details

• Java Version (java --version):
  java version "15" 2020-09-15
• Library Version in build.gradle:

dependencies {
  ...
  implementation 'com.github.NaikSoftware:StompProtocolAndroid:1.6.3'
}

• Screenshot:
  

[szakerx]

Try putting RxJava2 on your classpath.