I am writing a system which generates wallets on a per user basis. It must be capable to receive and send payments. So I have to keep the private keys encrypted on the system.

Generating the private and public key with bitcoinj worked like a charm. At the moment I am struggling a bit with the Wallet class in bitcoinj.

I do not want to have any threads or connections "outside" of my application. So I want to avoid the usage of the PeerGroup.

I would like to create an offline transaction and then broadcast it myself. For example via blockchain.info or other services.

How can I do this with bitcoinj? I am reading a lot through the API, but I am missing deeper tutorials for my case.