My answer on Quora to “Which is the best career path to choose, Oracle ADF, or Java?”
Concentrate on Oracle ADF. ADF skills are in high demand and pay better than pure Java skills.
Because Oracle ADF is a Java-based framework, you will need to learn some basic Java as you build you ADF skills. Once you land an ADF job, you will learn more Java as you work with ADF. This allows you to continue to pure Java or other frameworks if you are not happy with ADF.