这是我的第一个问题！
我的do-while菜单循环不能正确重复。
在用户将选项A或B输入信息后（而非X'退出'时，似乎每次重复打开交换机中的默认选项。而不是返回主菜单，也会打印默认开关以及另一个主菜单......
就像它收到了无效的输入但没有给出任何输入！
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 = '\0';
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);
}
}
这是打印输出我 BOLDED 是错误：
输入载体类型（M，C，LCV，HCV）：HCV 输入旅行时间（峰值，非高峰或夜晚）：夜晚
收费公路数据输入菜单
A - 第一选择 B - 第二选择 X - 退出
输入您的选择：A 输入旅行日期：6 输入入口点：5 输入退出点：3
收费公路数据输入菜单 A - 第一选择 B - 第二选择 X - 退出 输入您的选择：响应必须是单个字符！
注意没有响应输入
收费公路数据输入菜单
A - 第一选择 B - 第二选择 X - 退出
输入您的选择：a 输入旅行日期：2017年5月4日 输入入口点：5 输入退出点：2
收费公路数据输入菜单 A - 第一选择 B - 第二选择 X - 退出 输入您的选择：响应必须是单个字符！
注意没有响应输入
收费公路数据输入菜单
A - 第一选择 B - 第二选择 X - 退出
输入您的选择：x 退出数据输入菜单......
通行费：
（通行费总额：25.20美元）
细分费用：
（分解费用总额：0.00美元）
收费发票总计25.20
有人可以解释为什么会发生这种情况！
谢谢！
答案 0 :(得分：0)
问题可能出在sc.nextLine()来电后的sc.nextInt()来电中。由于sc.nextInt()不会使用\n换行符，这可能是您看到响应必须是单个字符的原因！错误。见这里：Scanner is skipping nextLine() after using next(), nextInt() or other nextFoo()?