Bitcoinj - A library for working with Bitcoin

bitcoinj is a library for working with the Bitcoin protocol. It can maintain a wallet, send/receive transactions without needing a local copy of Bitcoin Core and has many other advanced features.

Highly optimised lightweight simplified payment verification (SPV) mode. In this mode, only a small part of the block chain is downloaded, making bitcoinj suitable for usage on constrained devices like smartphones or cheap virtual private servers.