To find information about the classes in the Java library, go to:

The Java API web page (Java2 Standard Edition, version 1.3)
For example, to find out about the methods of the Rectangle class, first click on java.awt and then on Rectangle. This is exactly the same information, in the same format, that is available from the help menu in Kawa, once you donwload the Java documents from http://www.javasoft.com/products/jdk/1.2/download-docs.html .