A Little Java, A Few Patterns: What's New?

abstract class PizzaD { // 比萨饼 
    abstract PizzaD remA(); // 去除比萨饼中的凤尾鱼顶料 ( 因为太咸了 )
    abstract PizzaD topAwC(); // 在凤尾鱼顶料上加上奶酪顶料 ( 这样会盖住凤尾鱼的咸味 )
    abstract PizzaD subAbC(); // 将所有的凤尾鱼顶料换成奶酪顶料 
}

class Crust extends PizzaD { // 面包皮 
    PizzaD subAbC(){
        return new Crust();
    }
    PizzaD topAwC(){
        return new Crust();
    }
    PizzaD subAbC(){
        return new Crust();
    }
}

// 下面是各种顶料 
class Cheese extends PizzaD { // 奶酪 
    PizzaD p;
    Cheese (PizzaD _p) {
        p = _p;
    }
    PizzaD remA(){
        return new Cheese(p.remA());
    }
    PizzaD topAwC(){
        return new Cheese(p.topAwC());
    }
    PizzaD subAbC(){
        return new Cheese(p.subAbC());
    }
}

class Olive extends PizzaD { // 橄榄 
    PizzaD p;
    Olive (PizzaD _p) {
        p = _p;
    }
    PizzaD remA(){
        return new Olive(p.remA());
    }
    PizzaD topAwC(){
        return new Olive(p.topAwC());
    }
    PizzaD subAbC(){
        return new Olive(p.subAbC());
    }
}

class Anchovy extends PizzaD { // 凤尾鱼 
    PizzaD p;
    Anchovy (PizzaD _p) {
        p = _p;
    }
    PizzaD remA(){
        return p.remA();
    }
    PizzaD topAwC(){
        return new Cheese(new Anchovy(p.topAwC()));
    }
    PizzaD subAbC(){
        return new Cheese(p.subAbC());
    }
}

class Sausage extends PizzaD { // 香肠 
    PizzaD p;
    Sausage (PizzaD _p) {
        p = _p;
    }
    PizzaD remA(){
        return new Sausage(p.remA());
    }
    PizzaD topAwC(){
        return new Sausage(p.topAwC());
    }
    PizzaD subAbC(){
        return new Sausage(p.subAbC());
    }
}

class Spinach extends PizzaD { // 菠菜 
    PizzaD p;
    Spinach (PizzaD _p) {
        p = _p;
    }
    PizzaD remA(){
        return new Spinach(p.remA());
    }
    PizzaD topAwC(){
        return new Spinach(p.topAwC());
    }
    PizzaD subAbC(){
        return new Spinach(p.subAbC());
    }
}