My application is dealing with high speed RPC requests, so it cannot reply on synchronous blocking call to process requests. It wants web3j RPC calls to return tx hash immediately without blocking and invoke callback later after RPC completion. Can web3j do callback as follows as in web3js?
web3.eth.sendTransaction({data: code}, function(err, transactionHash) {
if (!err)
console.log(transactionHash); // "0x7f9fade1c0d57a7af66ab4ead7c2eb7b11a91385"
});