Need help on object array, please.

Question

Hello. I'm trying to write a program that stores student id numbers and their names into an array, and then prints them in numerical order. What I did was create an object called DSCC and put it in an array, but I'm having problems. Everytime I run this I get a null pointer exception, here is my code.
public class Main {
  public Main() {
  public void getStudenInfo(String Number1, String Name, int Number){
    Number1 = JOptionPane.showInputDialog("Enter student number, 999 to quit");
    Number = Integer.parseInt(Number1);
    if(Number != 999){
      Name = JOptionPane.showInputDialog("Enter student name");
  public void putInArray(DSCC ded[], String na, int nu){
      ded[0].studentname = na;
      ded[0].studentnumber = nu;
       System.out.println(ded[0]);
  public void printList(){
  public static void main(String[] args) {
    String name = "";
    String number1 = "";
    int number = 0;
    DSCC[] array = new DSCC[10];
    Main main1 = new Main();
    DSCC d = new DSCC();
     main1.getStudenInfo(number1, name, number);
     while(number != 999){
        main1.putInArray(array, name, number);
        main1.printList();
        main1.getStudenInfo(number1, name, number);
public class DSCC {
    String studentname;
    String number1;
    int studentnumber;
    public DSCC() {
}

Answer 1

There are a couple things i don't get about the code here but let me point out some thing that definately don't work.
The function getStudentInfo(...) does not change the value of its parameters Number1, Name and Number. You will need to redesign this method to get the entered values. I suggest breaking it up into three functions that return the value that the JOptionPane, like :
public String getStudentName(){
     return JOptionPane.showInputDialog("Enter Student Name :");
}And then replace the calls to getStudenInfo() with the three calls.
Also the array you make is not populated, which is probably the reason for the for the NPE. For example,
DSCC[] array = new DSCC[10];
//here come an NullPointerException
array[0].studentName = "Joe";
//can't do this... array[0] == null,  studentName does not exist!This happens in your code, though it is split up into different methods. If you trace through you will see that when you call the method putInArray(...) , the array's values are still null. For a fully intialized array, it should be:
DSCC[] array = new DSCC[10];
for(int i = 0; i < 10; i++) {
     array[0] = new DSCC();
array[0].studentName = "Joe";So at some point you need to initialize the values of the array.
Hope that helps....