Bitcoinj is not designed for building block explorers or web wallets where that kind of query is common, it's intended for building p2p apps that use local wallets. So that's why you can't figure out how to do it. You could extend the fully verifying store to build the extra indexes and some people have done exactly that, but they never contributed their code upstream.
Oh thank you very much , I wasted a lot of time keep trying .
And now I know ,with bitcoinJ, I have no way to conveniently check the balance of a giving "bitcoin address".
It only works like Bitcoin-Qt for personal usage. not for public search.
My question is there is a store class named DiskStoredBlock. what is this stand for ? doesn't that work for whole database?and any examples for the usage of this class?