code: @Override
      protected String documentation() {
          if (documentation == null) {
              JavaFileObject overviewPath = getOverviewPath();
              if (overviewPath == null) {
                  // no doc file to be had
                  documentation = "";
              } else {
                  // read from file
                  try {
                      documentation = readHTMLDocumentation(
                          overviewPath.openInputStream(),
                          overviewPath);
                  } catch (IOException exc) {
                      documentation = "";
                      env.error(null, "javadoc.File_Read_Error", overviewPath.getName());
                  }
              }
          }
          return documentation;
      }
docs: Do lazy initialization of "documentation" string.