The java api is a good site (you can download it, about 30mb zip)
http://java.sun.com/j2se/1.4.2/docs/api/index.html Depending on your
IDE, if you download and instal the api docs, then point
your IDE to where you've unzipped it, you can (generally) highlight the
class name, click on help/JDK help and the api page will open. You can then
go through all of the methods of the class (to see what they do), and check
for inherited methods - in this case dispose() is a method of Window.