GeometricObject 是一個抽象類，當我嘗試運行測試代碼（如下所示）時，我收到錯誤“無法實例化 GeometricObject 類型”任何想法如何解決它？  import geometricobject.GeometricObject;    public class TestGeometricObject {    public static void main(String[] args)    {        GeometricObject obj1 = new GeometricObject();        GeometricObject obj2 = new GeometricObject("blue", true);        System.out.println("Object 1: " + obj1.toString());        System.out.println("Object 2: " + obj2.toString());    }}