Remember to create and generate abi class for binding VM. abigen --abi SkyPetAbi.abi --bin SkyPet.bin --pkg SkyPet --lang java --out SkyPet.java

Here "SkyPet.bin" is the bytecode for the smart contract. There are some issues with this; see ethereum/go-ethereum#3286.

go get github.com/tools/godep $ cd $GOPATH/src/github.com/ethereum/go-ethereum $ godep go install ./cmd/abigen