Java applications run on the client from a web page are called Applets. Usually these run in a "sand box" - so don't have permission to do the things you want. However if you sign the Applet, you can give it the permissions you need.
You can also sign a Java Webstart application so that it has full access to the client machine.
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus