private String hash(String string) {
        final String sha1Hex = DigestUtils.sha1Hex(string);
        return StringUtils.substring(sha1Hex, 0, 8);
    }
private String hash ( String string ) { final String sha1Hex = DigestUtils . sha1Hex ( string ) ; return StringUtils . substring ( sha1Hex , 0 , 8 ) ; }
hash String with stable hash function
@param string to be hashed
@return hashed string