Reading from file - NullPointer exception

[Sage25]

Hello

I am reading in data from a file and creating objects with that data.
I have came across a NullPointerException which is really buggin me, i have tried everything!

What i intend on doing within my code is this:
Create a loop which reads in the data line by line.
With that line i am creating objects which will be stored in a temporary array of the object type
After the objects have been stored in the temporary array i am then calling a method which assigns that object to the class attribute


Heres my code for the reading in of file

//below reads lecturers
                 String [] LecturerField;//array to store data after read
                 Lecturer []sLecturer = new Lecturer[numL];// temp array of lecturers

                for (int i = 0; i < numL; i++) {
                   line = in.readLine();
                   if (line == null)
                    break;

                    LecturerField = line.split(",");
                    sLecturer[i] = new Lecturer(LecturerField[0], LecturerField[1], LecturerField[2],
                       Integer.parseInt(LecturerField[3]), Integer.parseInt(LecturerField[4]));
//line 185                    head.addLecturer(sLecturer[i]);
                    
            }

Heres the method which assigns the object to the class attribute

public void addLecturer(Lecturer lecturer){
//line 32 below
            if (numLecturers < lecturers.length) {
			lecturers[numLecturers++] = lecturer;
		}
	}

Here is my error when i try reading the file

xception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at UniversityModel.HeadOfSchool.addLecturer(HeadOfSchool.java:32)
        at UniversityModel.School.load(School.java:185)
        at GUI.Main.jMenuLoadActionPerformed(Main.java:142)
        at GUI.Main.access$000(Main.java:20)
        at GUI.Main$1.actionPerformed(Main.java:65)
        at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1849)
        at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2169)
        at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:420)
        at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:258)
        at javax.swing.AbstractButton.doClick(AbstractButton.java:302)
        at javax.swing.plaf.basic.BasicMenuItemUI.doClick(BasicMenuItemUI.java:1000)
        at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mouseReleased(BasicMenuItemUI.java:1041)
        at java.awt.Component.processMouseEvent(Component.java:5488)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3126)
        at java.awt.Component.processEvent(Component.java:5253)
        at java.awt.Container.processEvent(Container.java:1966)
        at java.awt.Component.dispatchEventImpl(Component.java:3955)
        at java.awt.Container.dispatchEventImpl(Container.java:2024)
        at java.awt.Component.dispatchEvent(Component.java:3803)
        at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4212)
        at java.awt.LightweightDispatcher.processMouseEvent(Container.java:3892)
        at java.awt.LightweightDispatcher.dispatchEvent(Container.java:3822)
        at java.awt.Container.dispatchEventImpl(Container.java:2010)
        at java.awt.Window.dispatchEventImpl(Window.java:1778)
        at java.awt.Component.dispatchEvent(Component.java:3803)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:463)
        at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
BUILD SUCCESSFUL (total time: 1 minute 51 seconds)

[Norm]

What variable is NULL at line 32? Check to see that your code has given it a value before you call the method.

[Sage25]

I'm guessing it would be the number of lecturers variable.
I have set this to 0 for the time being, but if i have no lecturers in the lecturer object array then the length would be 0 too, would i be correct in thinking that?

Here is the declaration for the array attribute which holds the lecturer objects

public class HeadOfSchool extends Lecturer {
	// Attributes
	private Lecturer[] lecturers;

[Norm]

private Lecturer[] lecturers

That defines a variable: lecturers but does NOT give it a value. It's value will be NULL. Your code needs to test if its null.

[Sage25]

Yes, i know.
Thats what i am trying to do is give the variable a value by reading in data from a file and assigning that data to an object then assign the object to the variable

[Norm]

Arrays need to be defined before they are used.
Lecturer[] lecturers = new Lecturer[5]; // create a 5 element array

Now lecturers is an array with 5 slots where you can put Lecturer objects.
lecturers[0] = new Lecturer(); // put a Lecturer object in slot 0