public Hash(String hex){
  if (hex.length() != 64) {
    throw new IllegalArgumentException("Digest length must be 64 hex characters for Hash");
  }
  this.bytes=ByteUtils.reverse(ByteUtils.fromHex(hex));
}

public Hash ( String hex ) { if ( hex . length ( ) != 64 ) { throw new IllegalArgumentException ( "Digest length must be 64 hex characters for Hash" ) ; } this . bytes = ByteUtils . reverse ( ByteUtils . fromHex ( hex ) ) ; }
create a hash from a hexadecimal representation of the digest note that this is in the reverse byte order of the internal binary representation .
