创建一个几何类型类，其中有计算面积getArea()和周长getPerimeter()抽象方法，然后通过它派生出三角形类、圆形类、矩形类，并通过测试类进行测试-Create a geometry type class, which calculated area getArea () and perimeter getPerimeter () abstract method, then it is derived from the triangle class, round type, rectangular type, and pass the test class to test