Prevent Java getting local IP?

Does anyone know how to prevent a Java applet from getting your IP
address, without disabling Java?

How does Java actually obtain your IP?  I have the code for doing this
but I'm interested in the actual mechanics behind it.

Is there any way to fake your own IP in order to "trick" Java into
getting a false IP?
Is it possible to disable the InetAddress.getLocalHost() function?