code: @Override
      public JavaFileObject getJavaFileForInput(JavaFileManager.Location location,
              String className,
              JavaFileObject.Kind kind)
              throws IOException {
          return stdFileManager.getJavaFileForInput(location, className, kind);
      }
docs: Returns a {@linkplain JavaFileObject file object} for input
  representing the specified class of the specified kind in the
  given location.
  
  @param location a location
  @param className the name of a class
  @param kind the kind of file, must be one of {@link
  JavaFileObject.Kind#SOURCE SOURCE} or {@link
  JavaFileObject.Kind#CLASS CLASS}
  @return a file object, might return {@code null} if the
  file does not exist
  @throws IllegalArgumentException if the location is not known
  to this file manager and the file manager does not support
  unknown locations, or if the kind is not valid
  @throws IOException if an I/O error occurred, or if {@link
  #close} has been called and this file manager cannot be
  reopened
  @throws IllegalStateException if {@link #close} has been called
  and this file manager cannot be reopened