Array null pointer exception error

Question

I am continuing with my project for school and have seemed to encounter another error. So what is happening is basically I am receiving a null pointer exception even though

Answer 1

As your code is currently written,

System.out.println(studentArray[0].getFirstName());

Will throw an NPE since you're never initializing the array.

private static students[] studentArray;

Just declares it, doesn't initialize it.

Maybe you should refactor your code as follows

private static ArrayList<students> studentArray = new ArrayList<students>();

// Inside the constructor or some method called before you access studentArray:
studentArray.add(stu1);
studentArray.add(stu2);
//...

// or, more concisely, since you're not using the temporary `students` variables:
studentArray.add(new students(65435, "Bob", "Ted"));
studentArray.add(new students(45546, "Guy", "Sid"));
//...

If you're committed to using an array and not a List,

private static students[] studentArray;

needs to be initialized with something like

private static students[] studentArray = new students[10];

and then you need to assign its elements

studentArray[0] = stu1;

or

studentArray[0] = new students(65435, "Bob", "Ted");

Answer 2

You should always create a object before trying to access it. You have declared a reference pointing to a array :

private static students[] studentArray;

but never assigned any object to the reference. Hence you get a NullPointerException.

Use this :

private static students[] studentArray = new students[size]; 

Above code will create a new object (array of students), pointed by a reference variable (studentArray). OR

You can use List or Set which are more efficient then array.