code: public String getCidr() {
          if (cidr != null) {
              return cidr;
          }
          if (ipAddress != null) {
              if (mask != null) {
                  return new SubnetUtils(ipAddress, mask).getCidrSignature();
              }
              if (cidrMask != null) {
                  return new SubnetUtils(ipAddress+cidrMask).getCidrSignature();
              }
          }
          return null;
      }
docs: Returns IP address in CIDR format.
  
  If specified {@code cidr} - returns {@code cidr} value.
  If specified {@code ipAddress} and {@code mask} - returns calculated IP address.
  If specified {@code ipAddress} and {@code cidrMask} - returns calculated IP address.
  Otherwise returns {@code null}
  
  @return ip address string representation in CIDR format