Is there any RPC Java library using which I can call lite coin methods? In case of bitcoin there is bitcoinj. but in Litecoin what will I use?
Litecoin has forked the Bitcoinj project so that you can use Litecoinj

Repo's are here: https://github.com/hank/litecoinj

and here : https://github.com/hank/litecoinj-new

I think the last one is the most recent and active repo.