code: public final void transform(final IClassTransformer transformer, final String directory) {
      transform(transformer, directory, directory, iterateClassnames(directory));
    }
docs: Search for class files on the passed directory name ({@link #iterateClassnames(String)}) and
  apply transformation to each one (
  {@link #transform(IClassTransformer, String, String, Iterator)}).
  
  <p>
  <strong>Limitation:</strong> do not search inside .jar files.
  </p>
  <p>
  If the passed {@code transformer} is {@code null} or the passed {@code directory} is
  {@code null} or empty nothing will transformed.
  </p>
  
  @param transformer the transformer that will apply transformations could be {@code null}.
  @param directory could be {@code null} or empty. The input and output directory are the same.
  
  @see #iterateClassnames(String)
  @see #transform(IClassTransformer, String, String, Iterator)