为什么会出现错误“类型的方法未定义”？

• Z时代
• 2024-01-10
• 分类：问答

我正在大学学习基础知识，并且希望对Eclipse中的以下错误有所帮助：“对于类型ShopCLI，未定义方法getCost（）”＆

"Exception in thread "main" java.lang.Error: Unresolved compilation problem:
    The method getCost() is undefined for the type ShopCLI
    at components.ShopCLI.main(ShopCLI.java:39)

这是我的代码

public class ShopCLI {
    public static void main(String[] args) {
        ArrayList<Order> ord = new ArrayList<>();
        System.out.println("Welcome to Sandwich Shop CLI V1!");
        System.out.println("Please Choose and Option by Typing the Appropriate Number from the List");
        System.out.println("1.New Order");
        Scanner sc = new Scanner(System.in);
        int choice = sc.nextInt();
        System.out.println("Please Choose an Outer From the List: ");
        System.out.println("Press 1 to Continue or 2 to Exit");
        int Sandwich = sc.nextInt();
        System.out.println("Outer Options are Bun, Bread or Brioche");
        String inputOuter = sc.next();
        System.out.println("Inner Options are Ham, Cheese or Cucumber");
        String inputInner = sc.next();
        System.out.println("Sauce Options are Mayo, Butter or Marmite");
        String inputSauce = sc.next();
        if (Sandwich == 1){
            ord.add(new Order(1, inputOuter, inputInner, inputSauce, 0));
            System.out.println("You Made a " + inputInner + " with " + inputSauce + " Sandwich on " + inputOuter);
            System.out.println("This Will Cost " + getCost());
        }
        else if (Sandwich == 2){
            System.out.println("Exited.");
        }
    }
}
public class Sandwich {
    //Fields
    ArrayList<Sandwich> sandwich = new ArrayList<>();
    String outer;
    String inner;
    String sauce;
    //Constructor
    public Sandwich(String outer, String inner, String sauce){
        this.outer = outer;
        this.inner = inner;
        this.sauce = sauce;
    }
    //Methods
    public String getOuter(){
        return outer;
    }
    public String getInner(){
        return inner;
    }
    public String getSauce(){
        return sauce;
    }
    public void setOuter(String repOuter){
        outer = repOuter;
    }
    public void setInner(String repInner){
        inner = repInner;
    }
    public void setSauce(String repSauce){
        sauce = repSauce;
    }
    public void createSandwich(String outer, String inner, String sauce){
        sandwich.add(new Sandwich(outer, inner, sauce));
    }
    public void setSandwich(String repOuter, String repInner, String repSauce){
        outer = repOuter;
        inner = repInner;
        sauce = repSauce;
    }
    public void resetOrder(){
        sandwich.removeAll(sandwich);
    }
}
public class Order extends Sandwich {
    //Fields
    int OrderId;
    double Cost;
    //Constructor
    public Order(int OrderId, String outer, String inner, String sauce, int Cost) {
        super(outer, inner, sauce);
        this.OrderId = OrderId;
        this.Cost = Cost;
    }
    //Methods
    public int getOrderId(){
        return this.OrderId;
    }
    public double getCost(){
        return this.Cost;
    }
    public void setOrderId(int repOrderID){
        this.OrderId = repOrderID;
    }
    public void overrideCost(int Cost){
        this.Cost = Cost;
    }
    public void setOrder(int repOrderId, String repOuter, String repInner, String repSauce){
        this.OrderId = repOrderId;
        this.outer = repOuter;
        this.inner = repInner;
        this.sauce = repSauce;
        double calcCost;
        double outerCost = 0;
        double innerCost = 0;
        double sauceCost = 0;
        //Outer Cost
        if(repOuter == "Bun")
        {
            outerCost = 0.5;
        }
        else if(repOuter == "Bread")
        {
            outerCost = 0.25;
        }
        else if(repOuter == "Brioche")
        {
            outerCost = 0.75;
        }
        else
        {
            System.out.println("Invalid Bread Type");
        }
        //Inner cost
        if(repInner == "Ham")
        {
            innerCost = 0.5;
        }
        else if(repInner == "Cheese")
        {
            innerCost = 0.25;
        }
        else if(repInner == "Cucumber")
        {
            innerCost = 0.75;
        }
        else
        {
            System.out.println("Invalid Filling Type");
        }
        //Sauce Cost
        if(repSauce == "Mayo")
        {
            sauceCost = 0.5;
        }
        else if(repSauce == "Butter")
        {
            sauceCost = 0.25;
        }
        else if(repSauce == "Marmite")
        {
            sauceCost = 0.75;
        }
        else
        {
            System.out.println("Invalid Sauce Type");
        }
        calcCost = outerCost + innerCost + sauceCost;
        this.Cost = calcCost;
    }
}

回答：

getCost方法是在订单类中定义的，而不是在ShopCLI类中定义的。所以你的代码：

ord.add(new Order(1, inputOuter, inputInner, inputSauce, 0));
System.out.println("You Made a " + inputInner + " with " + inputSauce + " Sandwich on " + inputOuter);
System.out.println("This Will Cost " + getCost());

应该改为

Order order = new Order(1, inputOuter, inputInner, inputSauce, 0);
ord.add(order);
System.out.println("You Made a " + inputInner + " with " + inputSauce + " Sandwich on " + inputOuter);
System.out.println("This Will Cost " + order.getCost());
                                       ^^^^^

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