JAVA do-while 开关打印菜单两次显示错误
JAVA Do-while switch prints menu twice display error
这是我的第一个问题！
我的 do-while 菜单循环没有正确重复。
似乎在用户将信息输入选项 A 或 B 后每次重复时都会在开关中打印默认选项（不是 X 'exiting'。而不是返回主菜单默认开关也与另一个主菜单一起打印...
好像收到了无效的输入，但是没有给出输入！
这是我的代码：
import java.util.Scanner;
public class Part3Final
{
static double rateM = 1.40;
static double rateC = 2.40;
static double rateLCV = 3.80;
static double rateHCV = 7.20;
static String M = "M";
static String C= ("C");
static String LCV ="LCV";
static String HCV = ("HCV");
static String Peak = "Peak";
static String offPeak = "Off-Peak";
static String Night = "Night" ;
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.print("\nEnter Vehicle Type (M, C, LCV, HCV):");
String vehicleType = sc.nextLine();
if (vehicleType.equals(HCV))
System.out.print("Enter Trip Time (Peak, Off-Peak or Night):");
String tripTime = sc.nextLine();
String choiceEntry;
String tripDetails="";
String tripList= "";
int sectors;
// Adjusted rate calculation
double adjustedHCVNight = (7.2 - (rateHCV*0.3));
double adjustedHCVPeak = ((rateHCV*0.4)+7.2);
// Variables to alter later
double adjustedSectorRate = 100;
double tripRate = 0;
double tripCharge= 0;
double totalCharge=0;
String breakList = "";
String breakReport = "";
double totalBreakCharge = 0;
//b char choiceEntryCh = '[=11=]';
do
{
System.out.println("\nToll Road Data Entry Menu");
System.out.println("-----------------------------------------");
System.out.println("\nA - First Option");
System.out.println("B - Second Option");
System.out.println("X - Exit");
System.out.print("\nEnter your selection: ");
choiceEntry = sc.nextLine();
choiceEntry = choiceEntry.toUpperCase();
if (choiceEntry.length() != 1)
System.out.println("Response must be a single character!");
else
switch (choiceEntry)
{
// equivalent of doing if (selection == 'A' || selection == 'a')
case "A":
case "a":
{
System.out.print("Enter Trip Date:");
String tripDate = sc.nextLine();
System.out.print("Enter Entry Point:");
int entryPoint = sc.nextInt();
System.out.print("Enter Exit Point:");
int exitPoint = sc.nextInt();
sectors= Math.abs(exitPoint-entryPoint);
if (tripTime.equals(Peak))
tripRate=(adjustedHCVPeak);
if (tripTime.equals(Night))
tripRate= (adjustedHCVNight) ;
if (tripTime.equals(offPeak))
tripRate= (rateHCV);
if (vehicleType.equals(M))
tripRate = rateM;
if (vehicleType.equals(C))
tripRate = rateC;
if (vehicleType.equals(LCV))
tripRate = rateLCV;
tripCharge= (tripRate * sectors);
tripDetails = String.format("%s %s %s %d %s %d %s %.2f %s %.2f %s", "- Trip on", tripDate, "from sector", entryPoint, "to sector", exitPoint, "at rate", tripRate, "(toll charge:", tripCharge,")");
tripList= (tripList + "\n" + tripDetails);
totalCharge= (totalCharge + tripCharge);
}
break;
case "B":
case "b":
{
System.out.print("\nEnter Breakdown Incident Date:");
String incidentDate = sc.nextLine();
System.out.print("Enter sector breakdown occured in:");
int breakdownPoint = sc.nextInt();
System.out.print("Enter vehicle recovery cost:");
double recoveryCost = sc.nextDouble();
breakReport = String.format("%s %s %s %d %s %.2f %s", "- Breakdown on", incidentDate, "in sector", breakdownPoint, "(recovery cost:", recoveryCost,")");
breakList= (breakList + "\n" + breakReport);
totalBreakCharge= (totalBreakCharge + recoveryCost);
}
break;
case "X":
case "x":
System.out.println("Exiting data entry menu...");
break;
default:
System.out.println("Error - invalid selection!");
break;
}
}while (!choiceEntry.equalsIgnoreCase("X"));
//if (choiceEntry.equals("X"))
//a System.out.println("Exiting data entry menu...");
System.out.printf("\n%-70s %s\n", "Toll Charges:\n", tripList);
System.out.printf("\n%s %.2f %s", "(Toll charge total: $",totalCharge,")");
System.out.printf("\n%-70s %s\n", "\nBreakdown Charges:\n", breakList);
System.out.printf("\n%s %.2f %s", "(Breakdown charge total: $",totalBreakCharge,")");
double totalInvoice= (totalCharge + totalBreakCharge);
System.out.printf("\n%-70s %.2f\n", "\nToll Invoice Total", totalInvoice);
}
}
这是我打印出来的 BOLDED 是错误：
输入车辆类型（M、C、LCV、HCV）：HCV
输入行程时间（高峰、非高峰或夜间）：夜间
收费公路数据输入菜单
A - 第一个选项
B - 第二个选项
X - 退出
输入您的选择：A
输入行程 Date:6
输入条目 Point:5
进入退出Point:3
收费公路数据输入菜单
A - 第一个选项
B - 第二个选项
X - 退出
输入您的选择：回复必须是单个字符！
请注意未输入回复
收费公路数据输入菜单
A - 第一个选项
B - 第二个选项
X - 退出
输入您的选择：一个
输入行程 Date:5/4/2017
输入条目 Point:5
进入退出Point:2
收费公路数据输入菜单
A - 第一个选项
B - 第二个选项
X - 退出
输入您的选择：回复必须是单个字符！
请注意未输入回复
收费公路数据输入菜单
A - 第一个选项
B - 第二个选项
X - 退出
输入您的选择：x
正在退出数据输入菜单...
通行费：
- 从第 5 区到第 3 区的 6 路旅行，费用为 5.04（通行费：10.08）
- 2017 年 5 月 4 日从第 5 区到第 2 区的旅行，费用为 5.04（通行费：15.12）
（通行费总计：25.20 美元）
故障费用：
（故障费用总计：0.00 美元）
通行费发票合计 25.20
谁能解释一下为什么会这样！
谢谢！
问题可能出在 sc.nextInt() 调用之后的 sc.nextLine() 调用中。由于 sc.nextInt() 不使用 \n 换行符，这可能就是您看到 Response must be a single character! 错误的原因。看这里：Scanner is skipping nextLine() after using next(), nextInt() or other nextFoo()?
这是我的第一个问题！
我的 do-while 菜单循环没有正确重复。
似乎在用户将信息输入选项 A 或 B 后每次重复时都会在开关中打印默认选项（不是 X 'exiting'。而不是返回主菜单默认开关也与另一个主菜单一起打印...
好像收到了无效的输入，但是没有给出输入！
这是我的代码：
import java.util.Scanner;
public class Part3Final
{
static double rateM = 1.40;
static double rateC = 2.40;
static double rateLCV = 3.80;
static double rateHCV = 7.20;
static String M = "M";
static String C= ("C");
static String LCV ="LCV";
static String HCV = ("HCV");
static String Peak = "Peak";
static String offPeak = "Off-Peak";
static String Night = "Night" ;
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.print("\nEnter Vehicle Type (M, C, LCV, HCV):");
String vehicleType = sc.nextLine();
if (vehicleType.equals(HCV))
System.out.print("Enter Trip Time (Peak, Off-Peak or Night):");
String tripTime = sc.nextLine();
String choiceEntry;
String tripDetails="";
String tripList= "";
int sectors;
// Adjusted rate calculation
double adjustedHCVNight = (7.2 - (rateHCV*0.3));
double adjustedHCVPeak = ((rateHCV*0.4)+7.2);
// Variables to alter later
double adjustedSectorRate = 100;
double tripRate = 0;
double tripCharge= 0;
double totalCharge=0;
String breakList = "";
String breakReport = "";
double totalBreakCharge = 0;
//b char choiceEntryCh = '[=11=]';
do
{
System.out.println("\nToll Road Data Entry Menu");
System.out.println("-----------------------------------------");
System.out.println("\nA - First Option");
System.out.println("B - Second Option");
System.out.println("X - Exit");
System.out.print("\nEnter your selection: ");
choiceEntry = sc.nextLine();
choiceEntry = choiceEntry.toUpperCase();
if (choiceEntry.length() != 1)
System.out.println("Response must be a single character!");
else
switch (choiceEntry)
{
// equivalent of doing if (selection == 'A' || selection == 'a')
case "A":
case "a":
{
System.out.print("Enter Trip Date:");
String tripDate = sc.nextLine();
System.out.print("Enter Entry Point:");
int entryPoint = sc.nextInt();
System.out.print("Enter Exit Point:");
int exitPoint = sc.nextInt();
sectors= Math.abs(exitPoint-entryPoint);
if (tripTime.equals(Peak))
tripRate=(adjustedHCVPeak);
if (tripTime.equals(Night))
tripRate= (adjustedHCVNight) ;
if (tripTime.equals(offPeak))
tripRate= (rateHCV);
if (vehicleType.equals(M))
tripRate = rateM;
if (vehicleType.equals(C))
tripRate = rateC;
if (vehicleType.equals(LCV))
tripRate = rateLCV;
tripCharge= (tripRate * sectors);
tripDetails = String.format("%s %s %s %d %s %d %s %.2f %s %.2f %s", "- Trip on", tripDate, "from sector", entryPoint, "to sector", exitPoint, "at rate", tripRate, "(toll charge:", tripCharge,")");
tripList= (tripList + "\n" + tripDetails);
totalCharge= (totalCharge + tripCharge);
}
break;
case "B":
case "b":
{
System.out.print("\nEnter Breakdown Incident Date:");
String incidentDate = sc.nextLine();
System.out.print("Enter sector breakdown occured in:");
int breakdownPoint = sc.nextInt();
System.out.print("Enter vehicle recovery cost:");
double recoveryCost = sc.nextDouble();
breakReport = String.format("%s %s %s %d %s %.2f %s", "- Breakdown on", incidentDate, "in sector", breakdownPoint, "(recovery cost:", recoveryCost,")");
breakList= (breakList + "\n" + breakReport);
totalBreakCharge= (totalBreakCharge + recoveryCost);
}
break;
case "X":
case "x":
System.out.println("Exiting data entry menu...");
break;
default:
System.out.println("Error - invalid selection!");
break;
}
}while (!choiceEntry.equalsIgnoreCase("X"));
//if (choiceEntry.equals("X"))
//a System.out.println("Exiting data entry menu...");
System.out.printf("\n%-70s %s\n", "Toll Charges:\n", tripList);
System.out.printf("\n%s %.2f %s", "(Toll charge total: $",totalCharge,")");
System.out.printf("\n%-70s %s\n", "\nBreakdown Charges:\n", breakList);
System.out.printf("\n%s %.2f %s", "(Breakdown charge total: $",totalBreakCharge,")");
double totalInvoice= (totalCharge + totalBreakCharge);
System.out.printf("\n%-70s %.2f\n", "\nToll Invoice Total", totalInvoice);
}
}
这是我打印出来的 BOLDED 是错误：
输入车辆类型（M、C、LCV、HCV）：HCV 输入行程时间（高峰、非高峰或夜间）：夜间
收费公路数据输入菜单
A - 第一个选项 B - 第二个选项 X - 退出
输入您的选择：A 输入行程 Date:6 输入条目 Point:5 进入退出Point:3
收费公路数据输入菜单 A - 第一个选项 B - 第二个选项 X - 退出 输入您的选择：回复必须是单个字符！
请注意未输入回复
收费公路数据输入菜单
A - 第一个选项 B - 第二个选项 X - 退出
输入您的选择：一个 输入行程 Date:5/4/2017 输入条目 Point:5 进入退出Point:2
收费公路数据输入菜单 A - 第一个选项 B - 第二个选项 X - 退出 输入您的选择：回复必须是单个字符！
请注意未输入回复
收费公路数据输入菜单
A - 第一个选项 B - 第二个选项 X - 退出
输入您的选择：x 正在退出数据输入菜单...
通行费：
- 从第 5 区到第 3 区的 6 路旅行，费用为 5.04（通行费：10.08）
- 2017 年 5 月 4 日从第 5 区到第 2 区的旅行，费用为 5.04（通行费：15.12）
（通行费总计：25.20 美元）
故障费用：
（故障费用总计：0.00 美元）
通行费发票合计 25.20
谁能解释一下为什么会这样！
谢谢！
问题可能出在 sc.nextInt() 调用之后的 sc.nextLine() 调用中。由于 sc.nextInt() 不使用 \n 换行符，这可能就是您看到 Response must be a single character! 错误的原因。看这里：Scanner is skipping nextLine() after using next(), nextInt() or other nextFoo()?