public boolean isCompletelyCollapsed(){
  if (collapsedUnder == null) {
    return false;
  }
  if (Math.abs(positionX - collapsedUnder.positionX) < COLLAPSE_TOLERANCE && Math.abs(positionY - collapsedUnder.positionY) < COLLAPSE_TOLERANCE) {
    return true;
  }
  return false;
}

public boolean isCompletelyCollapsed ( ) { if ( collapsedUnder == null ) { return false ; } if ( Math . abs ( positionX - collapsedUnder . positionX ) < COLLAPSE_TOLERANCE && Math . abs ( positionY - collapsedUnder . positionY ) < COLLAPSE_TOLERANCE ) { return true ; } return false ; }
say if the node is collapsed , and has reached the position of its parent .
