code: public Content getCrossClassLink(String qualifiedClassName, String refMemName,
                                      Content label, boolean strong, String style,
                                      boolean code) {
          String className = "";
          String packageName = qualifiedClassName == null ? "" : qualifiedClassName;
          int periodIndex;
          while ((periodIndex = packageName.lastIndexOf('.')) != -1) {
              className = packageName.substring(periodIndex + 1, packageName.length()) +
                  (className.length() > 0 ? "." + className : "");
              Content defaultLabel = new StringContent(className);
              if (code)
                  defaultLabel = HtmlTree.CODE(defaultLabel);
              packageName = packageName.substring(0, periodIndex);
              if (getCrossPackageLink(packageName) != null) {
                  /*
                  The package exists in external documentation, so link to the external
                  class (assuming that it exists).  This is definitely a limitation of
                  the -link option.  There are ways to determine if an external package
                  exists, but no way to determine if the external class exists.  We just
                  have to assume that it does.
                  */
                  DocLink link = configuration.extern.getExternalLink(packageName, pathToRoot,
                                  className + ".html", refMemName);
                  return getHyperLink(link,
                      (label == null) || label.isEmpty() ? defaultLabel : label,
                      strong, style,
                      configuration.getText("doclet.Href_Class_Or_Interface_Title", packageName),
                      "");
              }
          }
          return null;
      }
docs: ***********************************************************
  Return a class cross link to external class documentation.
  The name must be fully qualified to determine which package
  the class is in.  The -link option does not allow users to
  link to external classes in the "default" package.
  
  @param qualifiedClassName the qualified name of the external class.
  @param refMemName the name of the member being referenced.  This should
  be null or empty string if no member is being referenced.
  @param label the label for the external link.
  @param strong true if the link should be strong.
  @param style the style of the link.
  @param code true if the label should be code font.