Class Viewer is a lightweight, barebones tool designed to be the bare minimums needed to just do what you need--look up basic Java class information, especially public method info. And I've resisted the impulse to make it more complicated just to do something. But also if you are new to the Java language or just want to refresh on something it has a link to the Oracle Java Tutorial, where here is link: http://docs.oracle.com/javase/tutorial/
That is reached through Help menu on the Class Viewer app which also links to some instructions have done, including something short given by the app itself. For me will readily admit that routinely I find myself using the app to quickly refresh my Java skills. So like having such things handy. ___JSH, admin