code: private final static int defaultPort(String scheme) {
          if (scheme == null) {
              return -1;
          }
          Integer port = defaultPorts.get(scheme.trim().toLowerCase());
          return (port != null) ? port.intValue() : -1;
      }
docs: Return the default port used by a given scheme.
  
  @param the scheme, e.g. http
  @return the port number, or -1 if unknown