Calculate Hash SHA-256 for toutsurlebitcoin.fr

BlockHash.java

public static String calculateHash(Block block) {
  if (block != null) {
    MessageDigest digest = null;

    try {
      digest = MessageDigest.getInstance("SHA-256");
    } catch (NoSuchAlgorithmException e) {
      return null;
    }

    String txt = block.str();
    final byte bytes[] = digest.digest(txt.getBytes());
    final StringBuilder builder = new StringBuilder();

    for (final byte b : bytes) {
      String hex = Integer.toHexString(0xff & b);

      if (hex.length() == 1) {
        builder.append('0');
      }

      builder.append(hex);
    }

    return builder.toString();
  }

  return null;
}