用户

Question

我想让用户向现有的arraylist添加一个元素，并且使用一些与arraylist元素相关的变量，arraylist是：

所以我写了下面的代码：

           ArrayList<FruitShop> shops= new ArrayList<FruitShop>();
           Scanner in= new Scanner(System.in);

            FruitShop newShop = new FruitShop(null,0.0, new Apples(), new OwnerInfo());
            shops.add(newShop);
            System.out.println("What is the name of new shop?: ");
            newShop.setShopName(int.next());;
            System.out.println("Enter initial balance in USD: ");
            newShop.setBalance(Double.parseDouble(in.next()));
            System.out.println("Enter owner name: ");
            newShop.getShopOwner().setName(in.next());
            System.out.println("Enter owner age: ");
            newShop.getShopOwner().setAge(Integer.parseInt(in.next()));
            System.out.println("How many apples does the store have?: ");
            newShop.getApplesInfo().setQuantity(Integer.parseInt(in.next()));
            System.out.println("What is the price of each apple?:");
            newShop.getApplesInfo().setPrice(Double.parseDouble(in.next()));
            System.out.println("Your shop has been added! ");

           FruitShop.ID= ID;
            ID++;

这是从菜单中选择的东西＆＃34;添加一个新的水果店＆＃34;，所以每次用户添加水果店时，该对象将被称为newShop，然后旧的newShop将被删除！怎么能避免这个错误？ p.s：FruitShop由其他类组成：Apples和OwnerInfo 提前谢谢。

Answer 1

 ArrayList<FruitShop> shops= new ArrayList<FruitShop>();
           Scanner in= new Scanner(System.in);

            FruitShop newShop = new FruitShop(null,0.0, new Apples(), new OwnerInfo());

            System.out.println("What is the name of new shop?: ");
            newShop.setShopName(int.next());;
            System.out.println("Enter initial balance in USD: ");
            newShop.setBalance(Double.parseDouble(in.next()));
            System.out.println("Enter owner name: ");
            newShop.getShopOwner().setName(in.next());
            System.out.println("Enter owner age: ");
            newShop.getShopOwner().setAge(Integer.parseInt(in.next()));
            System.out.println("How many apples does the store have?: ");
            newShop.getApplesInfo().setQuantity(Integer.parseInt(in.next()));
            System.out.println("What is the price of each apple?:");
            newShop.getApplesInfo().setPrice(Double.parseDouble(in.next()));
            System.out.println("Your shop has been added! ");
             shops.add(newShop); // add last of the line when all initialization is done.

  

最后转移你的陈述shops.add(newShop);。初始化完成后。

Answer 2

完成所有shops.add(newShop);更改后，您必须插入行newShop。当然，将ArrayList<FruitShop> shops作为实例变量。每次调用方法后都不要创建新列表。

public class A {
    private List<FruitShop> shops= new ArrayList<FruitShop>();

    public void addShop() {
        ...
        shops.add(newShop);
    }
}