code: public static String cat (Object... components) {
          StringBuilder stringBuilder = new StringBuilder ();
          if (components.length > 0) {
              stringBuilder.append (components[0]);
              for (int i = 1; i < components.length; ++i) {
                  stringBuilder.append (BagObject.PATH_SEPARATOR).append (components[i].toString ());
              }
          }
          return stringBuilder.toString ();
      }
docs: Concatenate multiple string components to make a path
  @param components the different levels of the hierarchy to index
  @return a String with the components in path form for indexing into a bag object