问题
my instructions on the project were as followed:
Instructions: Use a sentinel value loop. To create a basic Rental Car Calculator
Ask each user for:
Type of vehicle (May use something other than strings, such as: 1 for an economy, 2 for a sedan, etc.) Days rented Calculate the (For each customer):
Rental cost, Taxes, Total Due. There are three different rental options with separate rates: Economy @ 31.76, sedan @ 40.32, SUV @ 47.56. [Note: only whole day units to be considered (no hourly rates)].
Sales tax is = to 6% on the TOTAL.
Create summary data with:
Number of customers Total money collected. Also, Include IPO, algorithm, and desk check values (design documents).
{WHAT I HAVE GOING AND MY QUESTION(S)}
package tests;
import java.util.InputMismatchException;
import java.util.Scanner;
public class Tester {
public static void main(String []args){
int count=0;
int days;
int cus = 10;
double DailyFee=0, NontaxTotal, CarType, Total,FullTotal=0;
boolean F1 = false, F2 = false, F3 = false;
Scanner in=new Scanner(System.in);
while (F3 == false) {
F3 = true;
System.out.print("Press 1 to enter Rental Calculator or else press 0 to quit\n");
System.out.println("Please only enter 1 or 0. Also, please only enter number(s) not letter(s)");
try {
cus=in.nextInt();
if (cus == 0 || cus == 1) {
F3 = true;
} else {
F3 = false;
System.out.println("Number must be either 1 or 0");
}
} catch (InputMismatchException ex) {
F3 = false;
System.out.println("Invalid entry");
in.next();
}
}
if(cus == 1) {
while(F1 == false) {
F1 = true;
count++;
System.out.print("What vehical would you like to rent?\n");
System.out.println("Enter 1 for an economy car");
System.out.println("Enter 2 for a sedan car");
System.out.println("Enter 3 for an SUV");
//
try {
CarType = in.nextInt();
if (CarType <= 0 || CarType >= 4) {
System.out.print("Number must be 1-3\n");
System.out.println("Please enter 1 for an economy car");
System.out.println("Enter 2 for a sedan car");
System.out.println("Enter 3 for an SUV");
F1 = false;
} else {
if (CarType == 1) {
F1 = true;
DailyFee=31.76;
} else if(CarType == 2) {
F1 = true;
DailyFee=40.32;
} else if(CarType == 3) {
F1 = true;
DailyFee=47.56;
}
while (F2 == false) {
F2 = true;
try {
System.out.print("Please enter the number of days rented. (Example; 3) : ");
days = in.nextInt();
if (days <= 0) {
System.out.println("Number of days must be more than zero");
F2 = false;
} else {
double x=days;
NontaxTotal = (DailyFee * x);
Total = (NontaxTotal * 1.06);
FullTotal+=Total;
F3 = true;
}
} catch(InputMismatchException ex) {
System.out.println("Answer must be a number");
F2 = false;
in.next();
}
}
}
} catch (InputMismatchException ex) {
F1 = false;
System.out.println("Answer must be a number");
}
}
}
in.close();
System.out.println("Count of customers : " + count);
System.out.printf("Total of the Day : $ %.2f", FullTotal);
}
}
{MY QUESTIONS}
When a letter is entered to the prompt "Press 1 to enter Rental Calculator or else press 0 to quit" it displays, an error prompt then the console asks for input again. Similarly, when a letter is inputted at the prompt "What vehicle would you like to rent?" the console continues to print lines with no stop? I do not know how to fix this?
I want my program to allow multiple calculation inputs to be made. However, after full calculation input (Days * Tax * Car Type) the console post summary data rather than looping? 2a. After the prompt "Please enter the number of days rented. (Example; 3) : " and following user input. How would I get my program to loop back to asking "Press 1 to enter Rental Calculator or else press 0 to quit"? with still making 0 prompt my summary data?
回答1:
Here you go, i modified it a bit and put the whole thing in a while loop (while (cus != 0)) now it is working perfectly, try this code and do let me know if you have questions
package inter;
import java.util.InputMismatchException;
import java.util.Scanner;
public class Inter {
public static void main(String []args){
int count=0;
int days;
int cus = 10; // added
double DailyFee=0, NontaxTotal, CarType, Total,FullTotal=0;
boolean F1 = false, F2 = false;
Scanner in=new Scanner(System.in);
while (cus != 0) {
while (true) {
System.out.println("If there are any customer press 1 else press 0");
try {
cus=in.nextInt();
if (cus == 0 || cus == 1) {
break;
} else {
System.out.println("Number must be either 1 or 0");
}
} catch (InputMismatchException ex) {
System.out.println("Invalid entry");
in.next();
}
}
if(cus == 1) {
while(F1 == false) {
F1 = true;
count++;
System.out.print("What vehical would you like to rent?\n");
System.out.println("Enter 1 for an economy car");
System.out.println("Enter 2 for a sedan car");
System.out.println("Enter 3 for an SUV");
try {
CarType = in.nextInt();
if (CarType <= 0 || CarType >= 4) {
System.out.print("Number must be 1-3\n");
System.out.println("Please enter 1 for an economy car");
System.out.println("Enter 2 for a sedan car");
System.out.println("Enter 3 for an SUV");
F1 = false;
} else {
if (CarType == 1) {
F1 = true;
DailyFee=31.76;
} else if(CarType == 2) {
F1 = true;
DailyFee=40.32;
} else if(CarType == 3) {
F1 = true;
DailyFee=47.56;
}
while (F2 == false) {
F2 = true;
try {
System.out.print("Please enter the number of days rented. (Example; 3) : ");
days = in.nextInt();
if (days <= 0) {
System.out.println("Number of days must be more than zero");
F2 = false;
} else {
//days = in.nextInt();
double x=days;
NontaxTotal = (DailyFee * x);
Total = (NontaxTotal * 1.06);
FullTotal+=Total;
}
} catch(InputMismatchException ex) {
System.out.println("Answer must be a number");
F2 = false;
in.next();
}
}
F2 = false;
}
} catch (InputMismatchException ex) {
F1 = false;
System.out.println("Answer must be a number");
in.next();
}
}
F1 = false;
}
}
System.out.println("Count of customers : " + count);
System.out.printf("Total of the Day : $ %.2f", FullTotal);
}
}
回答2:
I have just "refactored" your code a bit, removed some obsolete code and placed some other code on other locations. I've also used more clear naming for variables, and followed the naming conventions.
The problem you had, was that you did not in each catch block had a in.next(); meaning that while iterating, the variable kept using the same variable (which was invalid) so kept looping over the error messages.
Now this code is far from perfect, it can easily be improved still, but this should get you started.
package tests;
import java.util.InputMismatchException;
import java.util.Scanner;
public class Tester {
public static void main(String []args){
int count=0;
int days;
int cus;
int carType;
double dailyFee=0, nonTaxTotal, total,fullTotal=0;
boolean checkRunOrQuit = false, chooseTypeVehicle = false, numberOfDAysChosen = false;
Scanner in=new Scanner(System.in);
while ( !checkRunOrQuit ) {
System.out.print("Press 1 to enter Rental Calculator or else press 0 to quit\n");
System.out.println("Please only enter 1 or 0. Also, please only enter number(s) not letter(s)");
try {
cus=in.nextInt();
switch ( cus ) {
case 0: System.out.println("End of application");
System.exit(0); // This will actually end your application if the user enters 0, no need to verify later on
break;
case 1: checkRunOrQuit = true;
break;
default:
System.out.println("Number must be either 1 or 0");
}
} catch (InputMismatchException ex) {
System.out.println("Invalid entry: ");
in.next();
}
}
while( !chooseTypeVehicle ) { // --> simplified comparison
count++;
System.out.print("What vehical would you like to rent?\n");
System.out.println("Enter 1 for an economy car");
System.out.println("Enter 2 for a sedan car");
System.out.println("Enter 3 for an SUV");
try {
carType = in.nextInt();
chooseTypeVehicle = true;
switch ( carType ) {
case 1: dailyFee = 31.76;
break;
case 2: dailyFee = 40.32;
break;
case 3: dailyFee = 47.56;
break;
default:
System.out.print("Number must be 1-3\n");
System.out.println("Please enter 1 for an economy car");
System.out.println("Enter 2 for a sedan car");
System.out.println("Enter 3 for an SUV");
chooseTypeVehicle = false;
break;
}
} catch (InputMismatchException ex) {
System.out.println("Answer must be a number");
in.next(); // -> you forgot this one.
}
}
while ( !numberOfDAysChosen ) {
try {
System.out.print("Please enter the number of days rented. (Example; 3) : ");
days = in.nextInt();
if (days <= 0) {
System.out.println("Number of days must be more than zero");
} else {
nonTaxTotal = (dailyFee * days);
total = (nonTaxTotal * 1.06);
fullTotal+=total;
numberOfDAysChosen = true;
}
} catch(InputMismatchException ex) {
System.out.println("Answer must be a number");
in.next();
}
}
in.close();
System.out.println("Count of customers : " + count);
System.out.printf("total of the Day : $ %.2f", fullTotal);
}
}
来源：https://stackoverflow.com/questions/53058847/q-doing-multiple-loops-and-multiple-if-statements-and-if-else-statements-re