I want to use this tool: http://blockchain.info/pushtx to push transaction. I don't understand the input data. It says it is hex string representation. I've read information about that in the raw transaction of the RPC API, but I am working with bitcoinj, it there a way to get this hex string ?

Thank you

EDIT: I want to do that to compose and broadcast a transaction

For now I did this:

final StringBuilder sb = new StringBuilder();
Formatter formatter = new Formatter(sb);
try {
    ByteArrayOutputStream os = new ByteArrayOutputStream();
    transaction.bitcoinSerialize(os);
    byte[] bytes = os.toByteArray();
    for (byte b : bytes) {
        formatter.format("%02x", b);  
    }

    return sb.toString();
}catch (IOException e) {
    return "Couldn't serialize to hex string.";
} finally {
    formatter.close();
}