This is my .java that includes my main method:
package studentapp;
public class Studentapp {
public static ArrayList<Student> students = new <Student> ArrayList();
public static ArrayList snumbers = new ArrayList();
public static Scanner user = new Scanner(System.in);
public static int sncount = 0;
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
students.add(new Student("Kevin", "Swim", "AAS", 3.5));
students.add(new Student("Kyle", "Swim", "AAS", 2.8));
students.add(new Student("Bob", "Smith", "AAS", 2.8));
sncount = 1;
createArraynum();
createMenu();
}
private static void addastudent(){
System.out.println("First Name: " );
String fname = user.next();
System.out.println("Last Name: ");
String lname = user.next();
System.out.println("Major: ");
String major = user.next();
System.out.println("GPA: ");
double gpa = user.nextDouble();
Student a = new Student (fname,lname,major,gpa);
students.add(a);
a.sNumber = 1234500 + sncount;
snumbers.add(a.sNumber + sncount);
sncount ++;
createMenu();
}
private static void findaStudent(int input){
if (snumbers.contains(input)) {
for(Student i : students){
if(i.sNumber == input)
{System.out.println(i.sNumber +" " + i.firstName + " " + i.lastName +
" " + i.major + " gpa: " + i.gPA );
}
}
} else {
System.out.println("Sorry, The Student with that sNumber does not exist!");
}
createMenu();
}
private static void deleteaStudent(int input){
if (snumbers.contains(input)) {
for(Student i : students){
if(i.sNumber == input){
int number = students.indexOf(i);
students.remove(number);
System.out.println(i.sNumber +" "+ i.firstName+" "+i.lastName + " has been deleted!");
}
else { System.out.println(" ");}
}
} else {
System.out.println("Sorry, We cannot find a student with that number!");
}
}
private static void displayStudents(){
for(Student i : students){
System.out.println(i.sNumber +" " + i.firstName + " " + i.lastName +
" " + i.major + " gpa: " + i.gPA );
}
createMenu();
}
private static void displayNumStudent(){
System.out.println(students.size());
createMenu();
}
private static void exit(){
System.out.println("Thank you, Goodbye");
}
private static void createMenu(){
System.out.println("1. Add a Student");
System.out.println("2. Find a Student");
System.out.println("3. Delete a Student");
System.out.println("4. Display all Students");
System.out.println("5. Display the total number of students");
System.out.println("6. Exit");
System.out.println("Enter your Selection: ");
int count = user.nextInt();
switch (count){
case 1: addastudent();
break;
case 2: System.out.println("Find student with sNumber S");
int number = user.nextInt();
findaStudent(number);
break;
case 3: System.out.println("Delete student with sNumber S");
int number1 = user.nextInt();
deleteaStudent(number1);
break;
case 4: displayStudents();
break;
case 5: displayNumStudent();
break;
case 6: exit();
break;
default : System.out.println("Please Make a valid Selection");
createMenu();
}
}
private static void createArraynum(){
for(Student i : students){
i.sNumber = 1234500;
i.sNumber = i.sNumber + sncount;
snumbers.add(i.sNumber);
sncount ++;
}
}
}
and this is my Students Class.
public class Student {
String firstName;
String lastName;
int sNumber = 1234500;
String major;
double gPA;
int count;
public Student(String fName, String lName, String maj, double gpa){
firstName = fName;
lastName = lName;
major = maj;
gPA = gpa;
}
public String getFirstName(){
return this.firstName;
}
public String getLastName(){
return this.lastName;
}
public void setFirstName(String name){
this.firstName = name;
}
public void setLastName(String name){
this.lastName = name;
}
public int getSNumber(){
return this.sNumber;
}
public String getMajor(){
return this.major;
}
public void setMajor(String smajor){
this.major = smajor;
}
public double getGpa(){
return this.gPA;
}
public void setGpa(double num){
this.gPA = num;
}
@Override
public String toString(){
return firstName;
}
}
Everything seems to work the way i want it to. except when i try and call the deleteaStudent method. then i get errors if I try to remove the student from the arrayList students.
error looks like this:
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:859)
at java.util.ArrayList$Itr.next(ArrayList.java:831)
at studentapp.Studentapp.deleteaStudent(Studentapp.java:68)
at studentapp.Studentapp.createMenu(Studentapp.java:115)
at studentapp.Studentapp.main(Studentapp.java:28)
Java Result: 1
How can I get this to work properly?
