为什么不通过修改接口或者选择书写继承接口重写方法的新子类，偏偏选择添加上一个装饰器

package BiscuitsDemo;
public class BiscuitsTest {
    public static void main(String[] args) {
        //定义一个圆形烧饼对象
//        Biscuits biscuits = new RoundedBiscuits();    //使用多态啦
        RoundedBiscuits biscuits = new RoundedBiscuits();
        PetaloidBiscuits petaloidBiscuits = new PetaloidBiscuits(biscuits);
        petaloidBiscuits.rounded();
    }    
}
package BiscuitsDemo;
/**
 * 烧饼接口，定义烙印圆形烧饼抽象方法
 * @author 
 *
 */
public interface Biscuits {
    //烙印圆形烧饼
    void rounded();
}
package BiscuitsDemo;
/**
 * 圆形烧饼类（常见烧饼）
 * @author 
 *
 */
public class RoundedBiscuits implements Biscuits {
    @Override
    public void rounded() {
        System.out.println("新鲜出炉 圆乎乎的烧饼呀，圆乎乎");
    }
}
package BiscuitsDemo;
/**
 * 烧饼装饰抽象类
 * @author 
 *
 */
public abstract class DecoratorBiscuits implements Biscuits{
    Biscuits biscuits;        //定义烧饼接口对象，通过带参构造方法封装烧饼接口对象
    public DecoratorBiscuits(Biscuits biscuits) {
        this.biscuits = biscuits;
    }
}
package BiscuitsDemo;
/**
 * 添加了花瓣轮廓的烧饼烧饼类
 * @author 
 *
 */
public class PetaloidBiscuits extends DecoratorBiscuits{
    public PetaloidBiscuits(Biscuits biscuits) {
        super(biscuits);
    }
    @Override
    public void rounded() {
        //调用实际干活对象的rounded()方法
        biscuits.rounded();
        petaloid();　　　　//添加花瓣轮廓，扩展功能
    }
    //花瓣轮廓
    private void petaloid() {
        System.out.println("像花一样的烧饼来咯");
    }
}