我必须让我的课程代码进行验证。课程代码设置为1-7，选择必须在此范围内。每门课程价值3学分。用户无法注册超过9个学分。用户不能多次注册同一课程。我在重复课程代码时遇到了麻烦。
这是我的代码：
package u6a1_consoleregisterforcourse;
import java.util.Scanner;
public class U6A1_ConsoleRegisterForCourse {
public static void main(String[] args) {
System.out.println("Quenten's Copy");
Scanner input = new Scanner(System.in);
//choice is the current menu selection
//firstChoice is the first menu selection mande by the user
//secondChoice is the second menu selection mande by the user
//thirdChoice is the third menu selection mande by the user
// a choice of 0 means the choice has not been made yet
int choice;
int firstChoice = 0, secondChoice = 0, thirdChoice = 0;
int totalCredit = 0;
String yesOrNo = "";
do {
choice = getChoice(input);
switch (ValidateChoice(choice, firstChoice, secondChoice, thirdChoice, totalCredit)) {
case -1:
System.out.println("**Invalid** - Your selection of " + choice + " is not a recognized course.");
break;
case -2:
System.out.println("**Invalid** - You have already registerd for this " + ChoiceToCourse(choice) + " course.");
break;
case -3:
System.out.println("**Invalid** - You can not register for more than 9 credit hours.");
break;
case 0:
System.out.println("Registration Confirmed for course " + ChoiceToCourse(choice) );
totalCredit += 3;
if (firstChoice == 0)
firstChoice = choice;
else if (secondChoice == 0)
secondChoice = choice;
else if (thirdChoice == 0)
thirdChoice = choice;
break;
}
WriteCurrentRegistration(firstChoice, secondChoice, thirdChoice);
System.out.print("\nDo you want to try again? (Y|N)? : ");
yesOrNo = input.next().toUpperCase();
} while (yesOrNo.equals("Y"));
System.out.println("Thank you for registering with us");
}
public static int getChoice(Scanner input) {
System.out.println("Please type the number inside the [] to register for a course");
System.out.println("[1]IT4782\n[2]IT4784\n[3]IT4786\n[4]IT4789\n[5]IT2230\n[6]IT3345\n[7]IT3349");
System.out.print("Enter your choice : ");
return (input.nextInt());
}
//This method validates the user menu selection
//against the given registration business rules
//it returns the following code based on the validation result
// -1 = invalid, unrecognized menu selection
// -2 = invalid, alredy registered for the course
// -3 = invalid, No more than 9 credit hours allowed
// 0 = menu selection is valid
public static int ValidateChoice(int choice, int firstChoice, int secondChoice, int thirdChoice, int totalCredit) {
// TO DO - Add Code to:
// Validate user menu selection (the int choice method arguement)
// against the given registration business rules
int ValidateChoice;
if ((choice < 1) || (choice >= 8)){
ValidateChoice = -1;}
else if (secondChoice == firstChoice){
ValidateChoice = -2;}
else
{ValidateChoice = 0;}
return ValidateChoice;
}
public static void WriteCurrentRegistration(int firstChoice, int secondChoice, int thirdChoice) {
if (firstChoice == 0)
System.out.println("Current course registration: { none } " );
else if (secondChoice == 0)
System.out.println("Current course registration: { " + ChoiceToCourse(firstChoice) + " }" );
else if (thirdChoice == 0)
System.out.println("Current course registration: { " + ChoiceToCourse(firstChoice) +
", " + ChoiceToCourse(secondChoice) + " }");
else
System.out.println("Current course registration: { " + ChoiceToCourse(firstChoice) +
", " + ChoiceToCourse(secondChoice) + ", " + ChoiceToCourse(thirdChoice) + " }");
}
public static String ChoiceToCourse(int choice) {
String course = "";
switch (choice)
{
case 1:
course = "IT4782";
break;
case 2:
course = "IT4784";
break;
case 3:
course = "IT4786";
break;
case 4:
course = "IT4789";
break;
case 5:
course = "IT2230";
break;
case 6:
course = "IT3345";
break;
case 7:
course = "IT3349";
break;
default:
break;
}
return course;
}
}
我正在研究ValidateChoice方法。这是一项学术任务。
答案 0 :(得分：0)
最好摆脱那些firstChoice，secondChoice，thirdChoice变量并改为使用同类集合：
package u6a1_consoleregisterforcourse;
import java.util.*;
public class U6A1_ConsoleRegisterForCourse {
public static final int CREDITS_PER_COURSE = 3;
public static final int MAX_CREDITS = 9;
public static final int MAX_COURSES = MAX_CREDITS / CREDITS_PER_COURSE;
private final List<Integer> registeredCourses = new ArrayList<>(MAX_COURSES);
private int totalCredit;
public static void main(String[] args) {
System.out.println("Quenten's Copy");
U6A1_ConsoleRegisterForCourse registrar = new U6A1_ConsoleRegisterForCourse();
Scanner input = new Scanner(System.in);
//choice is the current menu selection
int choice;
String yesOrNo;
do {
choice = getChoice(input);
switch (registrar.validateChoice(choice)) {
case -1:
System.out.println("**Invalid** - Your selection of " + choice + " is not a recognized course.");
break;
case -2:
System.out.println("**Invalid** - You have already registered for this " + choiceToCourse(choice) + " course.");
break;
case -3:
System.out.println("**Invalid** - You can not register for more than " + MAX_CREDITS + " credit hours.");
break;
case 0:
System.out.println("Registration Confirmed for course " + choiceToCourse(choice));
registrar.totalCredit += CREDITS_PER_COURSE;
registrar.registeredCourses.add(choice);
break;
}
registrar.writeCurrentRegistration();
System.out.print("\nDo you want to try again? (Y|N)? : ");
yesOrNo = input.next().toUpperCase();
} while (yesOrNo.equals("Y"));
System.out.println("Thank you for registering with us");
}
private static final String[] courses = {"IT4782", "IT4784", "IT4786", "IT4789", "IT2230", "IT3345", "IT3349"};
public static String choiceToCourse(int choice) {
return courses[choice - 1];
}
public static int getChoice(Scanner input) {
System.out.println("Please type the number inside the [] to register for a course");
for (int i = 1; i <= courses.length; i++)
System.out.format("[%d]%s%n", i, choiceToCourse(i));
System.out.print("Enter your choice : ");
return (input.nextInt());
}
// This method validates the user menu selection
// against the given registration business rules
// it returns the following code based on the validation result
// -1 = invalid, unrecognized menu selection
// -2 = invalid, alredy registered for the course
// -3 = invalid, No more than 9 credit hours allowed
// 0 = menu selection is valid
public int validateChoice(int choice) {
if ((choice < 1) || (choice > courses.length))
return -1;
if (registeredCourses.contains(choice))
return -2;
if (totalCredit + CREDITS_PER_COURSE > MAX_CREDITS)
return -3;
return 0;
}
public void writeCurrentRegistration() {
StringBuilder sb = new StringBuilder("Current course registration: ");
if (registeredCourses.isEmpty())
sb.append(" { none }");
else {
sb.append("{ ");
boolean first = true;
for (int i : registeredCourses) {
if (first)
first = false;
else
sb.append(", ");
sb.append(choiceToCourse(i));
}
sb.append(" }");
}
System.out.println(sb);
}
}
答案 1 :(得分：0)
通过我给出的参数，并且只允许更改ValidateChoice方法，我能够接受John McClane的答案并将其转换为使其正常工作。我感谢你的帮助。我所做的很简单，现在才有意义。
这是：
public static int ValidateChoice(int choice, int firstChoice, int secondChoice, int thirdChoice, int totalCredit) {
// TO DO - Add Code to:
// Validate user menu selection (the int choice method arguement)
// against the given registration business rules
if ((choice < 1) || (choice >7))
return -1;
if ((choice == secondChoice) || (choice == firstChoice))
return -2;
if (totalCredit >= 9)
return -3;
return 0;
}
答案 2 :(得分：0)
您需要在代码中编写3种不同的验证：
public static int ValidateChoice(int choice, int firstChoice, int secondChoice, int thirdChoice, int totalCredit) {
//Validation: Choice is in range of 1 and 7
if(choice > 7 || choice < 1){
return -1;
}
// Validation : No 2 course choices have same value
boolean isInvalid = firstChoice!=0 ?
(firstChoice == secondChoice ||firstChoice == thirdChoice):
(secondChoice!=0 && secondChoice==thirdChoice);
if(isInvalid) {
return -2;
}
// Validation : Total credits are not more than 9
else if(totalCredit > 9){
return -3;
}
else{
return 0;
}
}
您的一位同学也在这里问了这个问题，
小心Pla窃