Cannot extend DefaultDocumentEvent. Any idea how to add functionality to basic editorpane edits?

I have an editorpane which displays editable information which changes based on what the user has selected in a list. So, for implementing my undo/redo feature I must first re-select the item that the user had selected when making their edits prior to undoing/redoing them. However, I am finding it difficult to add functionality to default document events because when I attempt to extend that class I get the "No enclosing instance" error.

below is my undomanager code. I know there is no setSelection and getCurrentSelection for JEditorPane but just pretend I am using an extended version with those features to determine what item the user has selected.

public class MyUndoManager extends UndoManager {

    private JEditorPane editor;

    public MyUndoManager() {
        super();
    }

    public void setEditor(JEditorPane editor) {
        this.editor = editor开发者_开发百科;
    }

    @Override
    public synchronized boolean addEdit(UndoableEdit anEdit) {
        if (anEdit instanceof javax.swing.text.AbstractDocument.DefaultDocumentEvent) {
            try {
                MyDocumentEvent evt = ((MyDocumentEvent) anEdit);
                evt.setCallbackObj(editor.getCurrentSelection());
                return super.addEdit(anEdit);
            } catch (Exception e) {
                e.printStackTrace();
                return false;
            }
        } else {
            return super.addEdit(anEdit);
        }
    }

    private class MyDocumentEvent extends javax.swing.text.AbstractDocument.DefaultDocumentEvent {

        private Object callbackObj;

        public void setCallbackObj(Object o) {
            this.callbackObj = o;
        }

        @Override
        public void undo() throws CannotUndoException {
            editor.setSelection(o);
            super.undo();
        }

        @Override
        public void redo() throws CannotRedoException {
            editor.setSelection(o);
            super.redo();
        }
    }
}

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It could be accessible by your code if DefaultDocumentEvent were static field of AbstractDocument.