Question

这个项目无法运行。请帮帮我。 http://pastebin.com/FX3JdUqb

IceCreamFlavor printPurchasedIceCreams() 这个方法只是返回ArrayList中的所有冰淇淋，下面是我的代码：

IceCreamShopMain.java：

public class IceCreamShopMain {
    public static void main(String[] args) {
        System.out.println(IceCreamFlavor.HAZELNUT.getName());
        System.out.println("The price of ice-cream is " + IceCreamFlavor.HAZELNUT.getPrice() + " dollars.");
        Customer c = new Customer(IceCreamFlavor.WHIPPEDCREAM);
        c.setCustomerName("Amy");
        Customer c2 = new Customer(IceCreamFlavor.ALMOND, "Mawson");        
        System.out.println(c.getCustomerName() + "`s purchased items are " + c.printPurchasedIceCreams() + ".");
        c.buy(IceCreamFlavor.OREOCOOKIECRUMBLES);
        System.out.println(c.printPurchasedIceCreams());
        System.out.println(c.icecream.getName());
        System.out.println(c2.getCustomerName() + " bought " + c2.icecream.getName() + "-Ice"
                + " which was " + c2.icecream.getPrice() + " dollars.");
        Customer c3 = new Customer(IceCreamFlavor.OREOCOOKIECRUMBLES, "Mickey");
        c3.buy(IceCreamFlavor.ALMOND);
        c3.buy(IceCreamFlavor.WHIPPEDCREAM);
        System.out.println(c3.printPurchasedIceCreams());

    }
}

Customer.java：

import java.util.*;
public class Customer {
    public IceCreamFlavor icecream;
    public int price;
    private String customerName;
    static String hamper;

    List<IceCreamFlavor> purchasedIceCreams = new ArrayList<IceCreamFlavor>();


    Customer(IceCreamFlavor icecream) {
        this.icecream = icecream;
    }

    Customer(IceCreamFlavor icecream, String customerName) {
        this.icecream = icecream;
        this.customerName = customerName;
    }

//  String getName() {
//      return icecream.getName();
//  }
//
//  int getPrice() {
//      return icecream.getPrice();
//  }

    String getCustomerName() {
        return this.customerName;
    }

    void setCustomerName(String customerName) {
        this.customerName = customerName;

    }

    void buy(IceCreamFlavor icecream) {
        // not really sure what business do here
        // just return the Ice cream.
//      this.icecream = icecream;
        purchasedIceCreams.add(icecream);

    }

     IceCreamFlavor printPurchasedIceCreams() {
        // not really sure what business do here
        // just return the Ice cream.
        for(int i = 0; i < purchasedIceCreams.size(); i++) {
            purchasedIceCreams.get(i);



        return purchasedIceCreams.get(i);


        }
     }
}

IceCreamFlavor.java：

enum IceCreamFlavor {

    HAZELNUT("Hazelnut", 300), WHIPPEDCREAM("WhippedCream", 270), ALMOND("Almond",
            370), OREOCOOKIECRUMBLES("OreoCookieCrumbles", 500), MARSHMALLOWS("Marshmallows", 420);

    public String name;
    public int price;

    private IceCreamFlavor(String name, int price) {
        this.name = name;
        this.price = price;
    }

    String getName() {
        return name;
    }

    int getPrice() {
        return price;
    }

}

错误日志：

线程“main”中的异常java.lang.Error：未解析的编译   问题：此方法必须返回IceCreamFlavor类型的结果

在Customer.printPurchasedIceCreams（Customer.java:45）at   IceCreamShopMain.main（IceCreamShopMain.java:8）此方法必须返回   IceCreamFlavor类型的结果

Answer 1

Java总是希望100％确定你在not void函数中返回一些东西。它可能发生在purchasedIceCreams.size() == 0，在这种情况下，执行不会进入printPurchasedIceCreams()中的for循环，所以不能保证你返回一些东西，这就是你得到Unresolved编译错误的原因：

IceCreamFlavor printPurchasedIceCreams() {
        for(int i = 0; i < purchasedIceCreams.size(); i++) {
            purchasedIceCreams.get(i);
            return purchasedIceCreams.get(i);
        }
}

您可以通过在for循环外部的函数末尾添加return null;或重新构建函数来快速解决问题。

IceCreamFlavor printPurchasedIceCreams() {
            for(int i = 0; i < purchasedIceCreams.size(); i++) {
                return purchasedIceCreams.get(i);
            }
            return null;
}

Here我发现了与您类似的问题，您可能需要查看以了解详情。

附注：这与错误无关，但不正确的做法是方法名称与其功能不匹配。您应该有两个单独的方法：printPurchasedIceCreams()方法执行所有打印但不返回任何内容，并使用getFirstPurchasedIceCream()方法返回第一个冰淇淋（或null）。

Answer 2

这还行吗？我感激不尽。

List<IceCreamFlavor> printPurchasedIceCreams() {
    // not really sure what business do here
    for (int i = 0; i < purchasedIceCreams.size(); i++) {
        System.out.println(purchasedIceCreams.get(i));

    }

    return purchasedIceCreams;

}

JAVA IceCreamProject无法运行

2 个答案: