one of my line having a problem with

package u8a1_2dconsoleregisterforcourse; import java.util.Scanner; public class U8A1_2DConsoleRegisterForCourse { public static void main(String[] args) { System.out.println("Teacher's Copy"); Scanner input = new Scanner(System.in); // courses 2d array hold course code and their credit hours String[][] courses = { { "IT1006", "IT4782", "IT4789", "IT4079", "IT2230", "IT3345","IT2249" }, { "6", "3", "3", "6", "3", "3", "6" }}; // validChoices 2d array holds valid number choices (as strings) // selected by user and their corresponding courses e.g //String[][] choices = { {"5", "IT2230"}, {"1", "IT1006"}, {"6","IT3345"} }; String[][] validChoices = { { "", "" }, { "", "" }, { "", "" } }; int choice; int totalCredit = 0; String yesOrNo = ""; do { choice = getChoice(courses, input); switch (ValidateChoice(choice, validChoices, totalCredit, courses)) { 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 "+ courses[0][choice - 1] + " 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 "+ courses[0][choice - 1]); totalCredit += Integer.parseInt(courses[1][choice - 1]); if (validChoices[0][0].equals("")) { validChoices[0][0] = Integer.toString(choice); validChoices[0][1] = courses[0][choice - 1]; } else if (validChoices[1][0].equals("")) { validChoices[1][0] = Integer.toString(choice); validChoices[1][1] = courses[0][choice - 1]; } else if (validChoices[2][0].equals("")) { validChoices[2][0] = Integer.toString(choice); validChoices[2][1] = courses[0][choice - 1]; } break; } WriteCurrentRegistration(validChoices, totalCredit); System.out.print(" Do you want to try again? (Y|N)? : "); yesOrNo = input.next().toUpperCase(); } while (yesOrNo.equals("Y")); System.out.println("Thank you for registering with us"); } // This method prints out the selection menu to the user in the form of // [selection number]Course Code (Course Credit Hours) // from the courses array one per line // and then prompts the use to make a number selection public static int getChoice(String[][] courses, Scanner input) { System.out.println("Please type the number inside the [] to register for a course"); System.out.println("The number inside the () is the credit hours for the course"); for (int i = 0; i < courses[0].length; i++){ System.out.println("[" + (i + 1) + "]" + courses[0][i] + "("+ courses[1][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 static int ValidateChoice(int choice, String[][] validChoices, int totalCredit, String[][] courses) { (this is the line i am having issue with ) String choiceAsString = Integer.toString(choice); if (choice < 1 || choice > 7) return -1; else if (choiceAsString.equals(validChoices[0][0]) || choiceAsString.equals(validChoices[1][0]) || choiceAsString.equals(validChoices[2][0])) return -2; else if ( totalCredit + Integer.parseInt(courses[1][choice-1]) > 9) return -3; return 0; } // This method prints the current list of registered courses thus far // from the courses array separated by , and enclosed inside { } // It also prints the total credit registered for thus far public static void WriteCurrentRegistration(String[][] validChoices, int totalCredit) { if (validChoices[0][0].equals("")) System.out.println("Current course registration: { none } "); else if (validChoices[1][0].equals("")) System.out.println("Current course registration: { "+ validChoices[0][1] + " }"); else if (validChoices[2][0].equals("")) System.out.println("Current course registration: { "+ validChoices[0][1] + ", " + validChoices[1][1] + " }"); else System.out.println("Current course registration: { "+ validChoices[0][1] + ", " + validChoices[1][1] + ", "+ validChoices[2][1] + " }"); System.out.println("Current registration total credit = " + totalCredit); } }