如何正确使用枚举来进行简单的价格计算（Java）

Question

我正在尝试优化一个看起来像这样的代码刺：

public class Kvarteret {
    public static final String ONE_BEER = "hansa";
    public static final String ONE_CIDER = "grans";
    public static final String REAL_BEER = "vestkyst";
    public static final String GT = "gt";
    public static final String BACARDI_SPECIAL = "bacardi_special";

    public int calculatePrice(String drink, boolean student, int amount) {

        if (amount > 2 && (drink == GT || drink == BACARDI_SPECIAL)) {
            throw new RuntimeException("Too many drinks, max 2.");
        }

        int price;

        if (drink.equals(ONE_BEER)) { price = 74;}
        else if (drink.equals(ONE_CIDER)) { price = 103;}
        else if (drink.equals(REAL_BEER)) { price = 110; }
        else if (drink.equals(GT)) { price = ingredient6() + ingredient5() + ingredient4();}
        else if (drink.equals(BACARDI_SPECIAL)) {
            price = ingredient6()/2 + ingredient1() + ingredient2() + ingredient3();
        } else { throw new RuntimeException("Item not in menu"); }

        if (student && (drink == ONE_BEER || drink == ONE_CIDER || drink == REAL_BEER)) { price = price - price/10;}
        return price*amount;
    }

    //rom unit
    private int ingredient1() { return 65;}

    // grenadine unit
    private int ingredient2() { return 10;}

    //lime-juice unit
    private int ingredient3() { return 10;}

    //mint-leafs unit
    private int ingredient4() { return 10; }

    //tonic-water unit
    private int ingredient5() { return 20; }

    //gin unit
    private int ingredient6() { return 85; }
}

代码是一个简单的程序，可以计算饮料的价格。我使用代码作为起点，因为他们似乎我们正在尝试做类似的事情。

到目前为止，我的代码看起来像这样：

import java.util.*;

public class Kvarteret2 {
    private static double price;
    private static double order;

    // Enums defines common values
    private enum Beer_Cider {
        BEER("Hansa", 74), CIDER("Grans", 103), REAL_BEER("Vestkyst", 110);

        private static String order;

        Beer_Cider(String order, double cost) {
            order = order;
            price = cost;
        }

        private static String getOrder() {return order;}
        private static double getCost() {return price;}
    }

    private enum DrinkIngredients {

        ROM("Rom", 65), GRENADINE("Grenadine", 10), LIME("Lime-juice", 10),
        MINT("Mint", 10), TONIC("Tonic-water", 20), GIN("Gin", 85);

        private static String ingredient;

        DrinkIngredients(String ingredient, double cost){
            ingredient = ingredient;
            price = cost;
        }

        private static String getIngredient() {return ingredient;}
        private static double getCost() {return price;}
    }

    // Dictionary with the drink as Key and a list of the ingredients and prices as value
    Map<String, List<DrinkIngredients>> Drinks = new HashMap<String, List<DrinkIngredients>>(); 

    public Kvarteret2() {
        Drinks.put("GT", [DrinkIngredients.GIN, DrinkIngredients.TONIC, DrinkIngredients.MINT]);

    }


    private static double calculate_price(String drink, boolean student, int amount){

        if (amount > 2) {
            throw new IllegalArgumentException("Too many drinks! You can order max 2 drinks at a time.");
        }

        double student_discount = 0.1;

        if (student){
            if (drink == "BEER" || drink == "CIDER" || drink == "REAL BEER") {
                price = amount * (price - price * student_discount);
            }
        }
        return price;
    }
}

由于此代码，我会遇到错误：

public Kvarteret2() {
    Drinks.put("GT", [DrinkIngredients.GIN, DrinkIngredients.TONIC, DrinkIngredients.MINT]);

}

我正在尝试将元素添加到字典中，但我认为这不是正确的方法。

我知道我的代码可能还没有100％优化，但是我只想在尝试使其变得更好之前是否可以使该解决方案起作用（因为很可能有更好的方法可以做到这一点）。

如何正确创建要使用枚举创建的字典？

Answer 1

您的代码中有很多错误。

您正在使用错误的语法来创建Java中的A list （它的工作方式与JavaScript ）的

[DrinkIngredients.GIN, DrinkIngredients.TONIC, DrinkIngredients.MINT] // <- that's not correct

List.of(DrinkIngredients.GIN, DrinkIngredients.TONIC, DrinkIngredients.MINT) // <- correct

工作方式相同 。特定的枚举恒定不应标记静态。修改器static表明在类的所有实例中共享一个字段，enum在一天结束时是类。如果您想要字符串order在各种饮料中都是唯一的，则该行不正确：

private static String order;

构造函数中的另一个错误：

Beer_Cider(String order, double cost) {
    order = order;
    price = cost;
}

line order = order = order = order; 在您时行不通预计。它不会将对象属性分配，而只是将参数重新分配给本身。您应该使用关键字 此 参考对象字段顺序。

private enum BeerCider {
    BEER("Hansa", 74), CIDER("Grans", 103), REAL_BEER("Vestkyst", 110);
    
    private String order;
    private double cost;
    
    Beer_Cider(String order, double cost) {
        this.order = order;
        this.cost = cost;
    }
    
    private String getOrder() {return order;}
    private double getCost() {return cost;}
}

有关 enums 的更多信息，请查看 此教程

sidenote：根据 /code>字段），但是enum的名称必须用骆驼盒beercider，例如类和接口的名称。

Answer 2

尽管您尚未提及您遇到的错误，但这就是您可以填充kvarteret2构造函数的方式：

// Dictionary with the drink as Key and a list of the ingredients and prices as value
    Map<String, List<DrinkIngredients>> Drinks = new HashMap<String, List<DrinkIngredients>>(); 
   List<DrinkIngredients> list=new ArrayList<DrinkIngredients>(); // define ArrayList outside constructor

public Kvarteret2() {
  list.add(DrinkIngredients.GIN);
  list.add(DrinkIngredients.TONIC);
  list.add(DrinkIngredients.MINT);
  Drinks.put("GT", ls);
}