从 Java 中的列表中显示特定类型披萨的方法

Question

我在 Java 中有一个简单的披萨程序，使用工厂模式制作。基本上，当工厂作为参数给出时，它会创建一个特定的比萨饼，然后将其添加到 PizzaShop 的比萨饼列表中。

我想创建一个方法来显示我有多少个特定的比萨饼。例如，当调用该方法时，我希望它显示类似“我们有 5 个 PizzaChicago 和 3 个 PizzaNewYork”的内容。我不知道该怎么做。

这是我的代码。

public interface Pizza {
    String name();
}

public class PizzaChicago implements Pizza{
    public Integer price;
    public PizzaChicago(Integer price){
        this.price = price;
    }

    @Override
    public String name() {
        return this.getClass().getSimpleName();
    }
}

public class PizzaNewYork implements Pizza{
    public Integer price;
    public PizzaNewYork(Integer price){
        this.price = price;
    }
    @Override
    public String name() {
        return this.getClass().getSimpleName();
    }
}


public interface PizzaFactory {
   public Pizza createPizza(Integer price);
}

public class PizzaNewYorkFactory implements PizzaFactory{
    @Override
    public Pizza createPizza(Integer price) {
        return new PizzaNewYork(6);
    }
}

public class PizzaChicagoFactory implements PizzaFactory{
    @Override
    public Pizza createPizza(Integer price) {
        return new PizzaChicago(8);
    }
}

import java.util.ArrayList;
import java.util.List;

public class PizzaShop {
    List<Pizza> pizzaList = new ArrayList<>();
    public void createPizza(PizzaFactory factory, Integer price){
        Pizza pizza = factory.createPizza(price);
       System.out.println(pizza.name() + " " + "was created");
        pizzaList.add(pizza);
    }

}
`

Answer 1

您需要做的是迭代列表并检查每个对象的类型。

int countPizzaNewYork = 0, countPizzaChicago = 0; 
for(Pizza p: pizzaList){
    if(p instanceOf PizzaNewYork)
    {
     countPizzaNewYork++;
    }
    else
    {
     countPizzaChicago++;
    }

 }
System.out.println("We have "+ countPizzaChicago+" PizzaChicago and "+countPizzaNewYork+" PizzaNewYork");

Answer 2

替代方法（使用 Map 而不是 List）：

public class PizzaShop {
    Map<String, Integer> pizzaDiary = new HashMap<>();

    public void createPizza(PizzaFactory factory, Integer price) {
        Pizza pizza = factory.createPizza(price);
        System.out.println(pizza.name() + " " + "was created");
        int previousCount = pizzaDiary.getOrDefault(pizza.name(), 0);
        pizzaDiary.put(pizza.name(), previousCount + 1);
    }
}

使用 pizzaDiary 地图打印出您的披萨数量。

Answer 3

每个披萨单独 class 可能会出现问题并且有些麻烦。并且对于某些使用 class name 和 instanceof 不是要走的路。您是否考虑过使用枚举来表示比萨饼？这是它可能如何工作的示例。

public class PizzaShopDemo {
    
    enum Pizza {
        CHICAGOPIZZA(8, "Chicago Pizza"),
        NEWYORKPIZZA(6, "New York Pizza");
        
        private double price;
        private String name;
        private int count = 0;
        
        private Pizza(double price, String name) {
            this.price = price;
            this.name = name;
        }
        
        public double getPrice() {
            return price;
        }
        
        public String getName() {
            return name;
        }
        
        public void update() {
            count++;
        }
        
        public int getCount() {
            return count;
        }
    }
    
    public static void main(String[] args) {
        
        new PizzaShopDemo().pizzaShop();
    }
    
    public void pizzaShop() {
        createPizza(Pizza.CHICAGOPIZZA);
        createPizza(Pizza.NEWYORKPIZZA);
        createPizza(Pizza.CHICAGOPIZZA);
        createPizza(Pizza.NEWYORKPIZZA);
        createPizza(Pizza.CHICAGOPIZZA);
        createPizza(Pizza.CHICAGOPIZZA);
        createPizza(Pizza.NEWYORKPIZZA);
        
        for (Pizza p : Pizza.values()) {
            System.out.println(p.getName() + ", " + p.getPrice()
                    + ", " + p.getCount());
        }
        
    }
    
    public void createPizza(Pizza type) {
        type.update();
        // other stuff here.
    }
}

版画

Chicago Pizza, 8.0, 4
New York Pizza, 6.0, 3

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