code: boolean processJarFile(String jarname, Collection<String> classNames) throws IOException {
          classPath.add(0, new File(jarname));
  
          if (classNames.isEmpty()) {
              return doJarFile(jarname);
          } else {
              return doClassNames(classNames);
          }
      }
docs: Processes named class files from the given jar file,
  or all classes if classNames is empty.
  
  @param jarname the name of the jar file to process
  @param classNames the names of classes to process
  @return true for success, false for failure
  @throws IOException if an I/O error occurs