public override void Remove(PhanTu ptu) { throw new Exception(); }
public override void Add(PhanTu ptu) { throw new Exception(); }
public override void Remove(PhanTu ptu) { this._phanTuCon.Remove(ptu); }
public override void Add(PhanTu ptu) { this._phanTuCon.Add(ptu); }
public abstract void Remove(PhanTu ptu);
public abstract void Add(PhanTu ptu);