BitcoinJ how to understand receive Address?
I'm not very familiar with bitcoinj but it appears to me that you need to do the following.

You're passed the transaction that was received (tx).  Call getOutputs to get a list of the transaction's outputs, and for each one, call getAddressFromP2PKHScript to determine the address credited by that output.

You should account for the possibility that there might be multiple outputs paying the same address, or multiple outputs paying different addresses that are in your wallet.