how can i feed more memory running a particular process such as java application server jboss.
What do you mean 'feed memory' to it? Processes request memory from the OS as they need it. The only case where you'd need to feed RAM to a process is if you're running out of RAM, in which case you need to go down to the shop and buy some more.
BTW when trying to determine free RAM don't be confused by the buffers/cache thing. Use the command 'free -m' to find out and look at the '+/-buffers/cache' line