Is there any (GUI) tool that I can use in this way? I start Java Application (Swing/AWT and/or JSP/servlet) and I can see which Java object (class) was called and which method in that class was called. And I can "travel" through this app and see how it was developed. ** I have source code. I ask this because I need to maintain and upgrade application that was develop by other people. Documentation was very bad and I can't figure out how it really works. I hope I make my problem clear! What is the best way to do this and which tool to use for this? Thanks.