java - 如何通过 String 方法将计算从辅助类导入到主类？

Question

我是java新手...我只想使用辅助类来计算汽车修理店的账单...取决于零件成本、工作时间和20%的增值税。我们认为每小时的费用为 20 美元。账单将在辅助类别内计算，程序将要求用户输入零件成本和工作时间。请通知我

package Exs2Lecture7;

import javax.swing.JOptionPane;

public class CarRepairApp {

    private static String partsStr; 
    private static String hoursStr;
    private static double parts = Double.parseDouble(partsStr);
    private static double hours = Double.parseDouble(hoursStr);
    private static double bill;
    private static CarRepair myRepair;

    public static void main(String[] args) 
    {
        CarRepair myRepair = new CarRepair(parts,hours);

        partsStr = read("Please enter the cost for the parts: ");
        hoursStr = read("Please enter the working hours: ");
    }

    public static String read (String prompt)
    {
        return (JOptionPane.showInputDialog(prompt));
    }
    public void display(String s)
    {
        this.bill = myRepair.calculateBill();
        JOptionPane.showMessageDialog(null, "The cost for the bill will be " + bill);
    }

}

辅助类将是

package Exs2Lecture7;

import javax.swing.*;

public class CarRepair 

{

    private double parts;
    private double hours;
    private static double HOURS_COST = 20;
    private static double VAT = 20;


    public CarRepair(double p, double h)
    {
        parts = p;
        hours = h;
    }

    public double calculateBill()
    {
        /*double bill = (parts + (hours * HOURS_COST)) + 
                ((parts + (hours * HOURS_COST)) * VAT/100);*/
        return ((this.parts + (this.hours * HOURS_COST)) + 
                ((this.parts + (this.hours * HOURS_COST)) * VAT/100));


    }
}

Answer 1

您需要解析字符串并将其转换为 double 。

double partsDouble= Double.parseDouble(partsStr);
double hoursDouble= Double.parseDouble(hoursStr);

然后创建 CarRepair 的实例，例如

CarRepair carRepair = new CarRepair(partsDouble,hoursDouble);

然后你可以调用calculateBill()方法

carRepair.calculateBill();

更新

@Blip 正确指出，无需创建另一个引用。 像这样更改你的 main

public static void main(String[] args) 
    {
        partsStr = read("Please enter the cost for the parts: ");
        hoursStr = read("Please enter the working hours: ");
        double partsDouble= Double.parseDouble(partsStr);
        double hoursDouble= Double.parseDouble(hoursStr);
        myRepair = new CarRepair(partsDouble,hoursDouble);
        myRepair.display();//no need to pass anything
    }