返回错误值的Java方法

我正在努力学习用Java正确地编写方法。我看过很多例子，看不出我做错了什么。我有一个名为InvoiceApp的主类，它使用一个名为Validator的类来筛选输入，然后是一个名为Invoice的类来处理用户输入。当InvoiceApp运行时，用户输入'r'或'c'作为客户类型，并输入双精度值作为“小计”。应用程序创建Invoice类的对象以使用getInvoice（）方法，该方法返回格式化的发票。 将返回格式化的发票，但字符串的值为空，所有数字的值为零（用户在第一位输入的数字除外）。Invoice类显然没有为变量赋值。我用了很多很多不同的方法，但都不能让它正常工作

有人能看出我做错了什么吗？这是我的密码：

InvoiceApp类：

import java.util.Scanner;

public class InvoiceApp
{    
public static void main(String[] args)
{
    // display a welcome message
    System.out.println("Welcome to the Invoice Total Calculator");
    System.out.println();  // print a blank line

    Scanner sc = new Scanner(System.in);
    String choice = "y";
    while(choice.equalsIgnoreCase("y"))
    {
        // get user entries
        String customerType = Validator.getString(sc,
            "Enter customer type (r/c):   ");
        double subtotal = Validator.getDouble(sc,
            "Enter subtotal:              ", 0, 10000);

        Invoice i;
        i = new Invoice(customerType, subtotal);
        System.out.println();
        System.out.println(i.getInvoice());

        System.out.println();
        System.out.print("Continue? (y/n): ");
        choice = sc.next();
        System.out.println();
    }
} 
}

发票类别：

import java.text.NumberFormat;

public class Invoice {
private final String customerType;
private final double subtotal;
private double discountAmount;
private double discountPercent;
private double invoiceTotal;
private String sCustomerType;

public Invoice(String customerType, double subtotal){
    this.customerType = customerType;
    this.subtotal = subtotal;
}
public void setDiscountPercent(double discountPercent){
    if (customerType.equalsIgnoreCase("r"))
    {
        if (subtotal >= 500)
            discountPercent = .2;
        else if (subtotal >= 250 && subtotal < 500)
            discountPercent =.15;
        else if (subtotal >= 100 && subtotal < 250)
            discountPercent =.1;
        else if (subtotal < 100)
            discountPercent =.0;
    }
    else if (customerType.equalsIgnoreCase("c"))
    {
            discountPercent = .2;
    }
    else
    {
        discountPercent = .05;
    }
}
public double getDiscountPercent(){
    return discountPercent;
}
public void setDiscountAmount(double discountAmount){
    discountAmount = subtotal * (getDiscountPercent());
}
public double getDiscountAmount(){
    return discountAmount;
}
public void setInvoiceTotal(double invoiceTotal){
    invoiceTotal = subtotal - (getDiscountAmount());
}
public double getInvoiceTotal(){
    return invoiceTotal;
}
public void setCustomerType(String sCustomerType){
    sCustomerType = "Unknown";
        if (customerType.equalsIgnoreCase("r"))
            sCustomerType = "Retail";
        else if (customerType.equalsIgnoreCase("c"))
            sCustomerType = "College";
}
public String getCustomerType(){
    return sCustomerType;
}
public String getInvoice(){
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    NumberFormat percent = NumberFormat.getPercentInstance();
    sCustomerType = this.getCustomerType();
    discountPercent = this.getDiscountPercent();
    discountAmount = this.getDiscountAmount();
    invoiceTotal = this.getInvoiceTotal();
    // Create a string representation of the full invoice and return
    String invoice = ("Subtotal:         " + currency.format(subtotal) + "\n"
                   + "Customer type:    " + sCustomerType + "\n"
                   + "Discount percent: " + percent.format(discountPercent)+ "\n"
                   + "Discount amount:  " + currency.format(discountAmount)+ "\n"
                   + "Total:            " + currency.format(invoiceTotal) + "\n");
    return invoice;
}
}

    import java.text.NumberFormat;

public class Invoice {
private final String customerType;
private double subtotal;
private double discountAmount;
private double discountPercent;
private double invoiceTotal;
private String sCustomerType;

public Invoice(String customerType, double subtotal){
    this.customerType = customerType;
    this.subtotal = subtotal;
}
public void setSubtotal(double subtotal){
    this.subtotal = subtotal;
}
public double getSubtotal(){
    return subtotal;
}
public void setDiscountPercent(double discountPercent){
    this.discountPercent = discountPercent;
}
public double getDiscountPercent(){
    if (customerType.equalsIgnoreCase("r"))
    {
        if (subtotal >= 500)
            discountPercent = .2;
        else if (subtotal >= 250 && subtotal < 500)
            discountPercent =.15;
        else if (subtotal >= 100 && subtotal < 250)
            discountPercent =.1;
        else if (subtotal < 100)
            discountPercent =.0;
    }
    else if (customerType.equalsIgnoreCase("c"))
    {
            discountPercent = .2;
    }
    else
    {
        discountPercent = .05;
    }
    return discountPercent;
}
public void setDiscountAmount(double discountAmount){
    this.discountAmount = discountAmount;
}
public double getDiscountAmount(){
    discountAmount = subtotal * (getDiscountPercent());
    return discountAmount;
}
public void setInvoiceTotal(double invoiceTotal){
    this.invoiceTotal = invoiceTotal;
}
public double getInvoiceTotal(){
    invoiceTotal = subtotal - (getDiscountAmount());
    return invoiceTotal;
}
public void setCustomerType(String sCustomerType){
    this.sCustomerType = sCustomerType;
}
public String getCustomerType(){
    sCustomerType = "Unknown";
        if (customerType.equalsIgnoreCase("r"))
            sCustomerType = "Retail";
        else if (customerType.equalsIgnoreCase("c"))
            sCustomerType = "College";
    return sCustomerType;
}
public String getInvoice(){
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    NumberFormat percent = NumberFormat.getPercentInstance();
    // Create a string representation of the full invoice and return
    String invoice = ("Subtotal:         " + currency.format(getSubtotal()) + "\n"
                   + "Customer type:    " + getCustomerType() + "\n"
                   + "Discount percent: " + percent.format(getDiscountPercent())+ "\n"
                   + "Discount amount:  " + currency.format(getDiscountAmount())+ "\n"
                   + "Total:            " + currency.format(getInvoiceTotal()) + "\n");
    return invoice;
}
}

导入java.text.NumberFormat；
公共类发票{
私有最终字符串customerType；
私人最终双倍小计；
私人双折扣；
私人双折；
私人双重发票总额；
私有字符串sCustomerType；
公共发票（字符串customerType，双倍小计）{
this.customerType=customerType；
这个。小计=小计；
}
公共无效设置折扣百分比（双倍折扣百分比）{
if（customerType.equalsIgnoreCase（“r”））
{
如果（小计>=500）
折扣百分比=.2；
否则如果（小计>=250&&小计<500）
折扣百分比=.15；
否则如果（小计>=100&&小计<250）
折扣百分比=.1；
否则，如果（小计<100）
折扣百分比=.0；
}
else if（customerType.equalsIgnoreCase（“c”））
{
折扣百分比=.2；
}
其他的
{
折扣百分比=.05；
}
}
公共双getDiscountPercent（）{
退货折扣百分比；
}
公共无效设置折扣挂载（双折扣挂载）{
折扣金额=小计*（getDiscountPercent（））；
}
公共双getDiscountAmount（）{
退货折扣额；
}
公共void setInvoiceTotal（双重invoiceTotal）{
invoiceTotal=小计-（getDiscountAmount（））；
}
公共双精度getInvoiceTotal（）{
退货发票总额；
}
public void setCustomerType（字符串sCustomerType）{
sCustomerType=“未知”；
if（customerType.equalsIgnoreCase（“r”））
sCustomerType=“零售”；
else if（customerType.equalsIgnoreCase（“c”））
sCustomerType=“学院”；
}
公共字符串getCustomerType（）{
返回sCustomerType；
}
公共字符串getInvoice（）{
NumberFormat currency=NumberFormat.getCurrencyInstance（）；
NumberFormat percent=NumberFormat.getPercentInstance（）；
sCustomerType=this.getCustomerType（）；
折扣百分比=this.getDiscountPercent（）；
discountAmount=this.getDiscountAmount（）；
invoiceTotal=this.getInvoiceTotal（）；
//创建完整发票和退货的字符串表示形式
字符串发票=（“小计：+货币.格式（小计）+”\n
+客户类型：“+sCustomerType+”\n
+折扣百分比：“+百分比.格式（折扣百分比）+”\n
+折扣金额：“+货币.格式（折扣金额）+”\n
+“总计：“+货币.格式（发票总计）+”\n”）；
退货发票；
}
}

验证程序类：

import java.util.Scanner;

public class Validator
{
public static String getString(Scanner sc, String prompt)
{
    System.out.print(prompt);
    String s = sc.next();  // read user entry
    sc.nextLine();  // discard any other data entered on the line
    return s;
}

public static int getInt(Scanner sc, String prompt)
{
    int i = 0;
    boolean isValid = false;
    while (isValid == false)
    {
        System.out.print(prompt);
        if (sc.hasNextInt())
        {
            i = sc.nextInt();
            isValid = true;
        }
        else
        {
            System.out.println("Error! Invalid integer value. Try again.");
        }
        sc.nextLine();  // discard any other data entered on the line
    }
    return i;
}

public static int getInt(Scanner sc, String prompt,
int min, int max)
{
    int i = 0;
    boolean isValid = false;
    while (isValid == false)
    {
        i = getInt(sc, prompt);
        if (i <= min)
            System.out.println(
                "Error! Number must be greater than " + min + ".");
        else if (i >= max)
            System.out.println(
                "Error! Number must be less than " + max + ".");
        else
            isValid = true;
    }
    return i;
}

public static double getDouble(Scanner sc, String prompt)
{
    double d = 0;
    boolean isValid = false;
    while (isValid == false)
    {
        System.out.print(prompt);
        if (sc.hasNextDouble())
        {
            d = sc.nextDouble();
            isValid = true;
        }
        else
        {
            System.out.println("Error! Invalid decimal value. Try again.");
        }
        sc.nextLine();  // discard any other data entered on the line
    }
    return d;
}

public static double getDouble(Scanner sc, String prompt,
double min, double max)
{
    double d = 0;
    boolean isValid = false;
    while (isValid == false)
    {
        d = getDouble(sc, prompt);
        if (d <= min)
            System.out.println(
                "Error! Number must be greater than " + min + ".");
        else if (d >= max)
            System.out.println(
                "Error! Number must be less than " + max + ".");
        else
            isValid = true;
    }
    return d;
}
}

import java.util.Scanner；
公共类验证器
{
公共静态字符串getString（扫描程序sc、字符串提示）
{
系统输出打印（提示）；
字符串s=sc.next（）；//读取用户条目
sc.nextLine（）；//放弃在该行中输入的任何其他数据
返回s；
}
公共静态int getInt（扫描程序sc，字符串提示）
{
int i=0；
布尔值isValid=false；
while（isValid==false）
{
系统输出打印（提示）；
if（sc.hasnetint（））
{
i=sc.nextInt（）；
isValid=true；
}
其他的
{
System.out.println（“错误！无效整数值。请重试”）；
}
sc.nextLine（）；//放弃在该行中输入的任何其他数据
}
返回i；
}
公共静态int getInt（扫描程序sc、字符串提示、，
整数最小值，整数最大值）
{
int i=0；
布尔值isValid=false；
while（isValid==false）
{
i=getInt（sc，提示符）；
如果（i=最大值）
System.out.println(
错误！数字必须小于“+max+”；
其他的
isValid=true；
}
返回i；
}
公共静态双getDouble（扫描程序sc，字符串提示）
{
双d=0；
布尔值isValid=false；
while（isValid==false）
{
系统输出打印（提示）；
if（sc.hasNextDouble（））
{
d=sc.nextDouble（）；
isValid=true；
}
其他的
{
System.out.println（“错误！十进制值无效。请重试”）；
}
sc.nextLine（）；//放弃在该行中输入的任何其他数据
}
返回d；
}
公共静态双getDouble（扫描程序sc、字符串提示、，
双最小值，双最大值）
{
双d=0；
布尔值isValid=false；
while（isValid==false）
{
d=getDouble（sc，提示符）；
如果（d=最大值）
System.out.println(
错误！数字必须小于“+max+”；
其他的
isValid=true；
}
返回d；
}
}

谢谢任何能帮忙的人

---

谢谢大家。我从setter方法中删除了参数并添加了这个。给施工人员。显然，我对两个主要方面感到困惑：

set方法中应该包含哪些参数？我试图插入set方法实际使用的变量，但也没有成功

我认为get方法只是用来返回set方法生成的值。因为二传手都是空的，所以他们

    import java.text.NumberFormat;

public class Invoice {
private final String customerType;
private double subtotal;
private double discountAmount;
private double discountPercent;
private double invoiceTotal;
private String sCustomerType;

public Invoice(String customerType, double subtotal){
    this.customerType = customerType;
    this.subtotal = subtotal;
}
public void setSubtotal(double subtotal){
    this.subtotal = subtotal;
}
public double getSubtotal(){
    return subtotal;
}
public void setDiscountPercent(double discountPercent){
    this.discountPercent = discountPercent;
}
public double getDiscountPercent(){
    if (customerType.equalsIgnoreCase("r"))
    {
        if (subtotal >= 500)
            discountPercent = .2;
        else if (subtotal >= 250 && subtotal < 500)
            discountPercent =.15;
        else if (subtotal >= 100 && subtotal < 250)
            discountPercent =.1;
        else if (subtotal < 100)
            discountPercent =.0;
    }
    else if (customerType.equalsIgnoreCase("c"))
    {
            discountPercent = .2;
    }
    else
    {
        discountPercent = .05;
    }
    return discountPercent;
}
public void setDiscountAmount(double discountAmount){
    this.discountAmount = discountAmount;
}
public double getDiscountAmount(){
    discountAmount = subtotal * (getDiscountPercent());
    return discountAmount;
}
public void setInvoiceTotal(double invoiceTotal){
    this.invoiceTotal = invoiceTotal;
}
public double getInvoiceTotal(){
    invoiceTotal = subtotal - (getDiscountAmount());
    return invoiceTotal;
}
public void setCustomerType(String sCustomerType){
    this.sCustomerType = sCustomerType;
}
public String getCustomerType(){
    sCustomerType = "Unknown";
        if (customerType.equalsIgnoreCase("r"))
            sCustomerType = "Retail";
        else if (customerType.equalsIgnoreCase("c"))
            sCustomerType = "College";
    return sCustomerType;
}
public String getInvoice(){
    NumberFormat currency = NumberFormat.getCurrencyInstance();
    NumberFormat percent = NumberFormat.getPercentInstance();
    // Create a string representation of the full invoice and return
    String invoice = ("Subtotal:         " + currency.format(getSubtotal()) + "\n"
                   + "Customer type:    " + getCustomerType() + "\n"
                   + "Discount percent: " + percent.format(getDiscountPercent())+ "\n"
                   + "Discount amount:  " + currency.format(getDiscountAmount())+ "\n"
                   + "Total:            " + currency.format(getInvoiceTotal()) + "\n");
    return invoice;
}
}

public void setDiscountPercent(double discountPercent){
    ...
        if (subtotal >= 500)
            discountPercent = .2;
    ...

public void setDiscountPercent(double discountPercent){
    ...
        if (subtotal >= 500)
            this.discountPercent = .2;
    ...

public void setDiscountAmount(double discountAmount){
    discountAmount = subtotal * (getDiscountPercent());
}

public void setDiscountAmount(double discountAmount){
    this.discountAmount = subtotal * (getDiscountPercent());
}