public void undo() throws CannotUndoException { if (canUndo() == false) { throw new CannotUndoException(); } hasBeenDone = false; }
public void undo() throws CannotUndoException { if (!canUndo()) throw new CannotUndoException(); hasBeenDone = false; }
	public void undo() throws CannotUndoException {		if (canUndo() == false) {			throw new CannotUndoException();		}		hasBeenDone = false;	} // undo()