code: public static Ipv4Range parse(String range) {
          int idx = range.indexOf(DASH);
          if (idx != -1) {
              Ipv4 start = Ipv4.parse(range.substring(0, idx));
              Ipv4 end = Ipv4.parse(range.substring(idx + 1, range.length()));
              return new Ipv4Range(start, end);
          } else {
              return parseCidr(range);
          }
      }
docs: Parses a <tt>String</tt> into an {@link Ipv4Range}.
  
  @param range a dash separated string of two IPv4 addresses e.g. "192.168.0.0-192.168.255.255"
  or a CIDR-notation string, e.g. "192.168.0.0/16"
  @return a new {@link Ipv4Range}
  @throws IllegalArgumentException if the string cannot be parsed
  @see #parseCidr(String)