code: @Override
      public boolean isSameFile(FileObject a, FileObject b) {
          return stdFileManager.isSameFile(b, b);
      }
docs: Compares two file objects and return true if they represent the
  same underlying object.
  
  @param a a file object
  @param b a file object
  @return true if the given file objects represent the same
  underlying object
  
  @throws IllegalArgumentException if either of the arguments
  were created with another file manager and this file manager
  does not support foreign file objects