为什么我收到错误“方法未定义类型”？

我正在大学学习基础知识，并希望得到Eclipse的以下错误的一些帮助：“方法getCost（）未定义类型ShopCLI”＆

"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 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 = 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; } } 

Answer 1

getCost方法在order类中定义，而不是在ShopCLI类中定义。 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()); ^^^^^ 

Answer 2

你必须从arraylist获取对象，然后访问方法：

 //get obj,then void System.out.println("This Will Cost " + ord.get(choise).getCost()); 

这将返回0，因为您在构造函数中设置了成本0：

 ord.add(new Order(1, inputOuter, inputInner, inputSauce, 0)); 

另外，将您的整数“三明治”命名为“三明治”而不用大写字母。 否则，看起来你的意思是“三明治”

Answer 3

在这一行：

 System.out.println("This Will Cost " + getCost()); 

…你没有指定你想要调用getCost()的东西，所以它在ShopCLI上调用它，因为那是调用发生的地方。 但ShopCLI没有getCost()方法。 您需要在订单上调用它：

 System.out.println("This Will Cost " + ord.get(0).getCost()); 

这是有效的，但是当你通过调用构造函数创建Order对象时，你不是在计算成本，而是设置传入的任何内容。将构造函数更新为：

  //Constructor public Order(int OrderId, String outer, String inner, String sauce) { super(outer, inner, sauce); this.OrderId = OrderId; double calcCost; double outerCost = 0; double innerCost = 0; double sauceCost = 0; //Outer Cost if(outer == "Bun") { outerCost = 0.5; } else if(outer == "Bread") { outerCost = 0.25; } else if(outer == "Brioche") { outerCost = 0.75; } else { System.out.println("Invalid Bread Type"); } //Inner cost if(inner == "Ham") { innerCost = 0.5; } else if(inner == "Cheese") { innerCost = 0.25; } else if(inner == "Cucumber") { innerCost = 0.75; } else { System.out.println("Invalid Filling Type"); } //Sauce Cost if(sauce == "Mayo") { sauceCost = 0.5; } else if(sauce == "Butter") { sauceCost = 0.25; } else if(sauce == "Marmite") { sauceCost = 0.75; } else { System.out.println("Invalid Sauce Type"); } calcCost = outerCost + innerCost + sauceCost; this.Cost = calcCost; } 

现在你的构造函数工作了，但是你必须删除你正在调用它的参数，所以将你的ord.add行更改为：

 ord.add(new Order(1, inputOuter, inputInner, inputSauce)); 

那应该是，如果我没有弄错的话。 但是，您可能需要考虑创建一个名为calculateCost的私有辅助方法，这样您就不会在构造函数和setOrder方法之间复制代码。

Answer 4

创建订单

 Order order = new Order(1, inputOuter, inputInner, inputSauce, 0); ord.add(order) // Add the order to your list. 

订单的成本由方法setOrder（int repOrderId，String repOuter，String repInner，String repSauce）设置

将此方法更改为以下内容。

 public void setOrder() { double calcCost; double outerCost = 0; double innerCost = 0; double sauceCost = 0; // Outer Cost if (outer.equalsIgnoreCase("Bun")) { outerCost = 0.5; } else if (outer.equalsIgnoreCase("Bread")) { outerCost = 0.25; } else if (outer.equalsIgnoreCase("Brioche")) { outerCost = 0.75; } else { System.out.println("Invalid Bread Type"); } // Inner cost if (inner.equalsIgnoreCase("Ham")) { innerCost = 0.5; } else if (inner.equalsIgnoreCase("Cheese")) { innerCost = 0.25; } else if (inner.equalsIgnoreCase("Cucumber")) { innerCost = 0.75; } else { System.out.println("Invalid Filling Type"); } // Sauce Cost if (sauce.equalsIgnoreCase("Mayo")) { sauceCost = 0.5; } else if (sauce.equalsIgnoreCase("Butter")) { sauceCost = 0.25; } else if (sauce.equalsIgnoreCase("Marmite")) { sauceCost = 0.75; } else { System.out.println("Invalid Sauce Type"); } calcCost = outerCost + innerCost + sauceCost; this.Cost = calcCost; } 

现在，您可以通过调用订单上的getCost（）来获得成本，如下所示。

要计算订单成本，请调用order.setOrder（）; 要获得订单成本，请调用order.getCost（）;

注意：不要使用==来比较字符串。 始终使用equals（）或equalsIgnoreCase（）。

Answer 5

我修改了ShopCLI类的代码

 package tester; import java.util.ArrayList; import java.util.Scanner; public class ShopCLI { public static void main(String[] args) { ArrayList ord = new ArrayList<>(); int orderNumber =1; System.out.println("Welcome to Sandwich Shop CLI V1!"); System.out.println("start order"); Scanner sc = new Scanner(System.in); while(true){ System.out.println("Press 1 for new order or 2 to Exit"); int choice = sc.nextInt(); if (choice == 1){ System.out.println("Enter outer Options:Outer Options are Bun, Bread or Brioche"); String inputOuter = sc.next(); System.out.println("Enter inner Options:Inner Options are Ham, Cheese or Cucumber"); String inputInner = sc.next(); System.out.println("Enter sauce Options:Sauce Options are Mayo, Butter or Marmite"); String inputSauce = sc.next(); Order order1 = new Order(orderNumber, inputOuter, inputInner, inputSauce, 0); order1.setOrder(inputOuter, inputInner, inputSauce); System.out.println("You Made a " + inputInner + " with " + inputSauce + " Sandwich on " + inputOuter); System.out.println("This Will Cost " + order1.getCost()); ord.add(order1); } else if (choice == 2){ System.out.println("Exited."); System.exit(1); } } } } 

并修改了setOrder方法的格式public void setOrder(String repOuter, String repInner, String repSauce)