如果从正确的“X”开始输入学生编号，然后继续使用该程序，我将如何让这段代码继续询问“学号”？
import java.util.Scanner;
public class SDevCA2 {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
//inputs
//Option 1
String userName;
String passWord1;
String passWord2;
String eol;
String userInput;
int loopVal =0;
char firstLetter = 'X';
int userOption;
final double FULLGRANT = 3000;
final double GRANTSEVENTYFIVE = 2250;
final double GRANTFIFTY = 1500;
double softWareGrade =0;
double mathsGrade =0;
double systemGrade =0;
double computerArchGrade =0;
double gradeCount;
final double SUBJECT_COUNT = 4;
double averageGrade;
int overallAverageResults;
int feesOwedPercent;
double feesOwedEuros;
//Option 2
double feesPaidByGrant =0;
double feesNotPaidByGrant =0;
int totalStudentsProcessed =0;
int totalStudentsRecievedGrant =0;
//Option 3
int studentsWith100Paid =0;
int studentsWith75Paid =0;
int studentsWith50Paid =0;
int studentsWithNoGrant =0;
int categoryMostStudents;
//End of Inputs
boolean run = true;
while ( run ) {
Scanner in = new Scanner (System.in);
//input of data
//input of data
System.out.println("Please enter your username: ");
userName = in.nextLine();
System.out.print("Please enter your password: ");
passWord1 = in.nextLine();
System.out.print("Please re-enter your password: ");
passWord2 = in.nextLine();
while (!passWord1.equals(passWord2))
{
System.out.println("Incorrect! Please try re-entering password ");
System.out.print("Please enter your password: ");
passWord1 = in.nextLine();
System.out.print("Please re-enter your password: ");
passWord2 = in.nextLine();
}
//ABC Grant Menu.
System.out.println("\n --------------------------------");
System.out.println ("Welcome to the ABC College Grant System \n 1. Calculate Grant \n 2. Fee Statistics \n 3. Grant Category Information \n 4. Exit");
userOption = in.nextInt();
//if Invalid Entry Error Message with the ABC Menu again
//Option 1
switch ( userOption ) {
case 1:
String studentName;
String studentNumber;
System.out.println ("Please Enter your Student Name: ");
studentName = in.next();
System.out.println ("Please Enter your Student Number: ");
userInput = in.next();
while ( userInput.charAt(0) == firstLetter) {
System.out.println("Correct");
break;
}
while ( userInput.charAt(0) != firstLetter)
{
System.out.println("No match, Student Numbr must begin with character capital X ");
}
{
//Error message if Student Number doesn't start with X
System.out.println ("What was your Grade in Software Development");
softWareGrade = in.nextDouble();
System.out.println ("What was your Grade in Maths");
mathsGrade = in.nextDouble ();
System.out.println("What was your Grade in Systems Analasys");
systemGrade = in.nextDouble ();
System.out.println("What was your Grade in Computer Archetecture");
computerArchGrade = in.nextDouble();
//Formula
gradeCount = softWareGrade + mathsGrade + systemGrade + computerArchGrade;
averageGrade = gradeCount / SUBJECT_COUNT;
//100% FEES PAID
if (averageGrade >=80 && averageGrade <=100) {
feesOwedPercent = 0;
feesOwedEuros = 0;
totalStudentsProcessed ++;
totalStudentsRecievedGrant ++;
studentsWith100Paid ++;
feesPaidByGrant = feesPaidByGrant + FULLGRANT;
System.out.println ("Student Name: " + studentName);
System.out.println ("Student Number: " + userInput);
System.out.println ("Average Grade: " +averageGrade);
System.out.println("Fees Owed: " +feesOwedPercent);
System.out.println("Fees not paid " + feesOwedEuros);
}
if (averageGrade >=60 && averageGrade <80 ) {
feesOwedPercent = 25;
feesOwedEuros = 750;
totalStudentsProcessed ++;
totalStudentsRecievedGrant ++;
studentsWith75Paid ++;
feesPaidByGrant = feesPaidByGrant + GRANTSEVENTYFIVE;
feesNotPaidByGrant = feesNotPaidByGrant + feesOwedEuros;
System.out.println ("Student Name: " + studentName);
System.out.println ("Student Number: " + userInput);
System.out.println ("Average Grade" +averageGrade);
System.out.println("Fees Owed: " +feesOwedPercent);
System.out.println("Fees not paid " + feesOwedEuros );
}
if (averageGrade >=40 && averageGrade <60) {
feesOwedPercent = 50;
feesOwedEuros = 1500;
totalStudentsProcessed ++;
totalStudentsRecievedGrant ++;
studentsWith50Paid ++;
feesPaidByGrant = feesPaidByGrant + GRANTFIFTY;
feesNotPaidByGrant = feesNotPaidByGrant + feesOwedEuros;
System.out.println ("Student Name: " + studentName);
System.out.println ("Student Number: " + userInput);
System.out.println ("Average Grade" +averageGrade);
System.out.println("Fees Owed: " +feesOwedPercent);
System.out.println("Fees not paid " + feesOwedEuros );
}
if ( averageGrade <40 ) {
feesOwedPercent = 100;
feesOwedEuros = 3000;
totalStudentsProcessed ++;
studentsWithNoGrant ++;
feesNotPaidByGrant = feesNotPaidByGrant + feesOwedEuros;
System.out.println ("Student Name: " + studentName);
System.out.println ("Student Number: " + userInput);
System.out.println ("Average Grade" +averageGrade);
System.out.println("Fees Owed: " +feesOwedPercent);
System.out.println("Fees not paid " + feesOwedEuros );
break;
}
switch ( userOption) {
case 2:
System.out.println("The overall fess paid by the grant: €" +feesPaidByGrant );
System.out.println("The overall fees not paid by the grant: €" +feesNotPaidByGrant );
System.out.println("The total number of students processed is: " +totalStudentsProcessed );
System.out.println("The total number of students who recieved a grant is: " +totalStudentsRecievedGrant );
break;
}
switch ( userOption ) {
case 3:
System.out.print("How many stduents are given grants in the following catergory");
System.out.println("100% Paid: " +studentsWith100Paid );
System.out.println("75% Paid: " +studentsWith75Paid );
System.out.println("50% Paid: " +studentsWith50Paid );
System.out.println("No Grant Paid: " +studentsWithNoGrant );
break;
}
switch ( userOption) {
case 4:
System.out.print("The number of stduents that are given grants in the following catergories: ");
System.out.println("\n");
System.out.println("100% Paid: " +studentsWith100Paid );
System.out.println("75% Paid: " +studentsWith75Paid );
System.out.println("50% Paid: " +studentsWith50Paid );
System.out.println("No Grant Paid: " +studentsWithNoGrant );
System.out.print("\n");
System.out.print("\n");
System.out.print("The catergory from which most grants are paid is: ");
run=false;
break;
default:
}
}
}
}
}
}
答案 0 :(得分：1)
用于提示用户输入学生编号然后接受他们输入的代码必须在while循环中。尝试这样的事情：
boolean validNumber = false;
while (!validNumber) {
System.out.println ("Please Enter your Student Number: ");
userInput = in.next();
if (userInput.charAt(0) == firstLetter) {
validNumber = true;
} else {
System.out.println("No match, Student Numbr must begin with character capital X ");
}
}