Plugins in Java

Hi
i need some information about how to use APIs or libraries developed by other companies as plugins in my java application. or how to create plugins of my own. is there any web-site etc where i can get some information?
Thanx in advance.
Padmanabh

If you are talking about Java libraries, you just need the jar files and information on the interfaces. The concept of "plugin" does not really apply.
Bill