Exception with spring-data-redis and spring-boot

Need some help with this issue I am facing: I am trying to run a spring-boot application with spring-data-redis in order to work with redis. I am getting this exception: Exception in thread "main" java.lang.NoSuchMethodError: org.springframework.data...

Who are some of the developers to follow on GitHub if you are interested in back-end development?

I am particularly interested in knowing about developers using Java, Python and Scala. Would also love to know about contributors to Machine Learning libraries.

What do you consider to be an ideal length of a method?