Google is pleased to announce the release of BitCoinJ, an implementation of the BitCoin system in Java. You can get it here under the Apache 2 license:
http://code.google.com/p/bitcoinj/It speaks the native p2p BitCoin protocol so does not rely on the JSON-RPC interface. It implements the "simplified payment verification" design outlined in Satoshis paper and as a result, is more suitable for mobile client developers than miners.
The library is not complete yet, but it's complete enough to send and receive coins.
BitCoinJ gives you:
- A reasonably easy to use API with full JavaDocs
- A getting started guide that takes you through one of the included ...
- Example apps, showing you how to do build a simple app with the library and how to solve Hals private key challenge.
- Unit tests and code with lots of comments. If you found it hard to understand the official implementation, try reading this one.
Please be aware of the following caveats:
- Both the API and the on-disk Wallet format will change in future releases. If you want to switch a wallet from this version of the library to another version, you'll probably have to send the coins between the two.
- The core block chain handling is not complete. It does not persist headers or block locators to disk yet, so every time you start your app it will redownload the block chain from scratch. It does not handle forks in the chain yet, this is coming in the next release.
- There are unit tests but the coverage isn't as high as I'd like. There'll be more in future.
- I'm really a C++ programmer by background so undoubtably some things could be more java-ish than they are.
I want this implementation to be as easy to understand as possible especially for people who aren't familiar with C++. If you aren't sure how to accomplish something, functionality you need isn't a part of the public API, or part of the code confuses you, let me know and I'll try to make it clearer.
The code is in Subversion and patches are welcome! Please post them either here in this forum, to the bitcoinj Google Group, or (better) using the Google Code review functionality.
