I create my own ClassLoader and use it load another application---one java class with main method. Another application has a lot of help files. In order to run this new application, I have to set up classpath dynamically for these help classes. As I know, I should override/overload method findLibrary(), it can set up classpath dynamically, and when I load class with main, it will find my help classes as library(e.g. my library:help.jar and help2.jar), so I can really run a new application from my old application. But how to overload or override method findLibrary() ?? I have no idea ?? Thanks for help.