如何在数组对象上调用获取方法-Java

Question

我有2个类，在Sumusercart中，我初始化对象的数组，然后我必须在Productcart中调用productid in ProductiD的方法，任何解决方案吗？

数据位于列表

List<SumUserCart> cartList

Sumusercart类中：

public class SumUserCart {
    int userId;
    ProductsCart[] products;

    public SumUserCart(int userId, ProductsCart[] products) {
        this.userId = userId;
        this.products = products;
    }

    @Override
    public String toString() {
        return "SumUserCart{" +
                "userId=" + userId +
                ", products=" + Arrays.toString(products) +
                '}';
    }

    public ProductsCart[] getProducts() {
        return products;
    }
 
   //getters & setters here
}

Productcart类：

public class ProductsCart {
    int productId;
    int quantity;


    @Override
    public String toString() {
        return "ProductsCart{" +
                "productId=" + productId +
                ", quantity=" + quantity +
                '}';
    }

    public ProductsCart() {}

    public ProductsCart(int productId, int quantity) {
        this.productId = productId;
        this.quantity = quantity;
    }

    //getters & setters here
}

这是我的功能，我试图打印产品ID的位置：

private static void printTheCart(List<SumUserCart> cartList){
        for (SumUserCart cartsByUser : cartList) {
            System.out.println("User Id: " + cartsByUser.getUserId() + " = " + Arrays.toString(cartsByUser.getProducts()));
            //System.out.println(cartsByUser.getProducts());
        }

    }

Answer 1

与数组的方式一样！使用索引值访问。
由于您想从ArrayList访问以下代码：

//get 0th element of cartList, which will be a SumUserCart object
SumUserCart suc = cartList.get(0);
//creating productsCarts object array:
ProductsCarts[] pc = suc.getProducts();
//Now use getProductId() method:
int pid = pc[0].getProductId(0);

Answer 2

那是称呼这个的正确方法

private static void printTheCart(List<SumUserCart> cartList){
        for (SumUserCart cartsByUser : cartList) {
            System.out.println("User Id: " + cartsByUser.getUserId() + " = " + Arrays.toString(cartsByUser.getProducts()));
            ProductsCart[] pcx = cartsByUser.getProducts();
            for (ProductsCart pc : pcx)
                System.out.println(pc.getProductId());
                
        }