@Override
  public void dispose() {
    if (myDropTarget != null) {
      DnDManager.getInstance().unregisterTarget(myDropTarget, myTree);
      myDropTarget = null;
    }
    if (myDragSource != null) {
      DnDManager.getInstance().unregisterSource(myDragSource, myTree);
      myDragSource = null;
    }
    myTree = null;
    myTreeStructure = null;
  }
@Override
  public void dispose()