Undo functionality in JTextArea

I am trying to implement undo functionality in JTextArea. Googled for tutorial and followed one of the tutorial and wrote the below code. The event is triggered when Ctrl+Z key is pressed. Its not working for me. Am I missing something?

private void undoActionPerformed(java.awt.event.ActionEvent evt) {
    Document doc = editorTextArea.getDocument();
    final UndoManager undo = new UndoManager();

    doc.addUndoableEditListener(new UndoableEditListener() {
        @Override
        public void undoableEditHappened(UndoableEditEvent e) {
            undo.addEdit(e.getEdit());
        }
    });
}