Question

我有两个接口和两个类，Order类是CoffeeBagOrder的父级，没有编译器错误，只是没有显示，我看不到为什么

订单类：

dd(session()->all())

CoffeeBagOrder类

public abstract class Order implements OrderInterface {
    //variables
    final static double SALES_TAX = 0.1; //not initialised by constructor
    int unitWeight, numberOfUnits;

    public Order() {
        unitWeight=0;
        numberOfUnits=0;
    }

    public Order(int unitWeight, int numberOfUnits) {
        unitWeight=unitWeight;
        numberOfUnits=numberOfUnits;
    }


    public void numberOfItems(int number) {
        numberOfUnits=number;

    }

    public void unitWeight(int weight) {
        unitWeight=weight;

    }



}

主要

public class CoffeeBagOrder extends Order implements Sales {

    final static double PRICE_PER_KG = 5.55;

    double salesBeforeTax;
    double tax;
    double totalSales;

    public CoffeeBagOrder() {

    }

    public CoffeeBagOrder(int unitWeight, int numberOfUnits) {
        super(unitWeight,numberOfUnits);


    }

    public double calculateSalesBeforeTax() {
        salesBeforeTax= unitWeight*numberOfUnits*5.50;
        return salesBeforeTax;
    }


    public double calculateSalesTax() {
        tax=salesBeforeTax*0.10;
        return tax;
        }



        public double calculateTotalSales() {
        totalSales=salesBeforeTax+tax;
        return totalSales;

    }
    //Override
    public String toString() {
        return "Price before tax: "+calculateSalesBeforeTax()+"\nTax: "+calculateSalesTax()+"\nTotal price: "+calculateTotalSales();
    }


}

我已经省略了接口，但是相应地遵循了它们，在此先感谢您，我也不确定我是否有效地编写了构造函数，因为它们都是相同的？

Answer 1

按如下所示更改您的Order类构造函数（选中此复选框）：

public Order(int unitWeight, int numberOfUnits) {
        this.unitWeight=unitWeight;
        this.numberOfUnits=numberOfUnits;
    }

您没有在构造函数中更新类字段！它正在为其分配参数。

并按如下所示修改CoffeeBagOrder中的toString（检查注释）：

@Override
    public String toString() {
        return "Price before tax: "+calculateSalesBeforeTax()+"\nTax: "+calculateSalesTax()+"\nTotal price: "+calculateTotalSales();
    }

当您打算覆盖时，始终使用@Override注释以使其生效，这是最佳实践，而不是显式调用toString（）。

并使用

打印

System.out.println(customer);

toString不输出，简单的层次结构类程序

1 个答案: