private static boolean isHexDigit(char c) {
        return (c >= 'A' && c <= 'F') || (c >= '0' && c <= '9');
    }
Write a printable representation of a byte array. Non-printable characters are hex escaped in
the format \\x%02X, eg: \x00 \x05 etc

@param b   array to write out
@param off offset to start at
@param len length to write
@return string output
stroom-bytebuffer/src/main/java/stroom/bytebuffer/hbase/Bytes.java