Java程序无法正确输出

Question

我的代码有点麻烦，我似乎无法弄明白。每当我运行它时，它会打印“Customer is null”而不是插入其名称。它也总是将所有税计算为0（我的if语句有问题吗？）。 你们有没有机会发现这个问题？好像其他一切都正常。 （在Customer类中编写方法，在TestCustomer类中调用它们，并且说明在帖子的末尾）。

感谢任何花时间阅读本文并尝试提供帮助的人。很抱歉这么多信息，我不知道造成这种情况的原因，所以我想我会包括所有内容。

客户类

import java.util.Scanner;

import javax.swing.JOptionPane;


public class Customer {
public static double taxRate = 0.00;
public static double saleRate = 0.00;
String customerName;
double listSaleAmount;
double saleDiscount = 0;
double netSaleAmount;
double taxAmount;
double saleTotal;
boolean taxable;
public double total;

public Customer (String customerName, boolean taxable) {

}

public void calculateTax () {
    saleDiscount = listSaleAmount*(saleRate/100);
    netSaleAmount = listSaleAmount-saleDiscount;

    if (taxable = true){
    taxAmount = netSaleAmount*(taxRate/100);
    }
    else{
        taxAmount = 0;
    }

    saleTotal = netSaleAmount + taxAmount;

    total += saleTotal;


}

public void printRecord () {
    System.out.println("Customer is " + customerName);
    System.out.println("Sale amount is $" + listSaleAmount);
    System.out.println("Discount amount is $" + saleDiscount);
    System.out.println("Net Sale Amount is $" + netSaleAmount);
    System.out.println("Tax amount is $" + taxAmount);
    System.out.println("Total Sale Amount is $" + saleTotal);
    System.out.println(" ");
}

public static void changeTaxAmount () {
    Scanner input = new Scanner(System.in);
    double userTaxAmount = Double.parseDouble(JOptionPane.showInputDialog("What is the Tax Rate? (8.25 & 8.50 for testing)"));
    taxRate = userTaxAmount;    
}

public static void changeSaleRate () {
    Scanner input = new Scanner(System.in);
    double userSaleAmount = Double.parseDouble(JOptionPane.showInputDialog("What is the Sale Discount Rate? (0.00 & 7.50 for testing)"));
    saleRate= userSaleAmount;

}

public static void printTaxRate() {
    System.out.println("Tax Rate is " + taxRate + "%.");
}

public static void printSaleRate() {
    System.out.println("The Sale Rate is " + saleRate + ".");
    System.out.println(" ");
}
}

TestCustomer类

public class TestCustomer {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

Customer customer1 = new Customer("Annie Smith", true);
Customer customer2 = new Customer("Bob Wilson", false);


Customer.changeTaxAmount();

Customer.printTaxRate();


Customer.changeSaleRate();

Customer.printSaleRate();

customer1.listSaleAmount = 65.00;
customer2.listSaleAmount = 52.00;


customer1.calculateTax();
customer1.printRecord();

customer2.calculateTax();
customer2.printRecord();


Customer.changeTaxAmount();
Customer.printTaxRate();
Customer.changeSaleRate();
Customer.printSaleRate();

customer1.listSaleAmount = 84.00;
customer2.listSaleAmount = 105.00;
customer1.calculateTax();
customer1.printRecord();
customer2.calculateTax();
customer2.printRecord();

double total2 = customer1.total + customer2.total;
System.out.println("The total of all sales is $" + total2);
    }

}

作业单（不用担心现在打印到文件，只是想让主要的机制工作）

另外，感谢那些帮助我完成关于这个项目的最后一个问题的人。你帮了很多忙。

Answer 1

在你的构造函数

中

public Customer (String customerName, boolean taxable) {

}

您传入了参数，但从未将它们分配给您的类字段。

尝试

public Customer (String customerName, boolean taxable) {
    this.customerName = customerName;
    this.taxable = taxable;
}

Answer 2

Customer类中的构造函数应将名称和应税值分配给Customer数据成员。

public Customer (String customerName, boolean taxable) {
    this.customerName = customerName;
    this.taxable = taxable;
}

Answer 3

您必须在customer类中定义构造函数以设置customerName和texable类级变量的值：

public Customer (String customerName, boolean taxable) {
  this.customerName = customerName;
  this.taxable = taxable;
}

此外，如果条件如下，似乎存在以下问题：

if (taxable = true){

您应该使用==运算符进行比较：

if (taxable == true) {

实际上，您无需比较它。只需使用：

if (taxable) {

Answer 4

不要使用if (taxable = true)，只需使用if (taxable)即可。