Help! nullpointerexception?

[Schillers]

Hi guys,

I am trying to create a method to read data from a saved file to load names from a file and display them in the listbox. I keep getting this error, can anyone help?

public void loadStaffMembers()
    {
        JFileChooser objFileDialogue = new JFileChooser();
        int intDialogResult = JFileChooser.CANCEL_OPTION;
        intDialogResult = objFileDialogue.showOpenDialog(this);
        
        if(intDialogResult == JFileChooser.APPROVE_OPTION)
        {
            File objFile = objFileDialogue.getSelectedFile();
            
            if(objFile.exists() && objFile.canRead())
            {
                try(ObjectInputStream objIn = new ObjectInputStream(
                        new BufferedInputStream(
                        new FileInputStream(objFile))))
                {
                    Object objData = objIn.readObject();
                    StaffList objNewStaffList = (StaffList)objData;
                    
                    if(objNewStaffList != null)
                    {
                        ArrayList<IObserver> objStaffListObservers = 
                                staffMembers.getObservers();
                        
                        for(IObserver currObserver : objStaffListObservers)
                        {
                            staffMembers.removeObserver(currObserver);
                        }
                        
                        for(IObserver currObserver : objStaffListObservers)
                        {
                            objNewStaffList.registerObserver(currObserver);
                        }
                        staffMembers = objNewStaffList;
                        staffMembers.notifyObservers();
                    } else
                    {
                        JOptionPane.showMessageDialog(this, "No staff members found!", "Error reading file", JOptionPane.ERROR_MESSAGE);
                    }
                }
                catch(ClassNotFoundException | IOException | ClassCastException ex)
                {
                    JOptionPane.showMessageDialog(this, "Data file could not be read", "Operation failed", JOptionPane.ERROR_MESSAGE);
                }
            } else {
                JOptionPane.showMessageDialog(this, "File not found/unreadable", "Error accessing file", JOptionPane.ERROR_MESSAGE);
            }
        } else {
            JOptionPane.showMessageDialog(this, "File load cancelled", "Operation aborted", JOptionPane.INFORMATION_MESSAGE);
        }
        
    }

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at leaveDataModel.StaffList.getObservers(StaffList.ja va:25)
at leaverecords.gui.staffMembers.loadStaffMembers(sta ffMembers.java:345)
at leaverecords.gui.staffMembers.mnuLoadActionPerform ed(staffMembers.java:388)
at leaverecords.gui.staffMembers.access$500(staffMemb ers.java:22)
at leaverecords.gui.staffMembers$6.actionPerformed(st affMembers.java:161)
at javax.swing.AbstractButton.fireActionPerformed(Abs tractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed (AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed (DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultB uttonModel.java:259)
at javax.swing.AbstractButton.doClick(AbstractButton. java:376)
at javax.swing.plaf.basic.BasicMenuItemUI.doClick(Bas icMenuItemUI.java:833)
at javax.swing.plaf.basic.BasicMenuItemUI$Handler.mou seReleased(BasicMenuItemUI.java:877)
at java.awt.Component.processMouseEvent(Component.jav a:6505)
at javax.swing.JComponent.processMouseEvent(JComponen t.java:3321)
at java.awt.Component.processEvent(Component.java:627 0)
at java.awt.Container.processEvent(Container.java:222 9)
at java.awt.Component.dispatchEventImpl(Component.jav a:4861)
at java.awt.Container.dispatchEventImpl(Container.jav a:2287)
at java.awt.Component.dispatchEvent(Component.java:46 87)
at java.awt.LightweightDispatcher.retargetMouseEvent( Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(C ontainer.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Conta iner.java:4422)
at java.awt.Container.dispatchEventImpl(Container.jav a:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719 )
at java.awt.Component.dispatchEvent(Component.java:46 87)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.j ava:723)
at java.awt.EventQueue.access$200(EventQueue.java:103 )
at java.awt.EventQueue$3.run(EventQueue.java:682)
at java.awt.EventQueue$3.run(EventQueue.java:680)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:696)
at java.awt.EventQueue$4.run(EventQueue.java:694)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPri vilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java: 693)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:244)
at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:151)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:147)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:139)
at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:97)

[DarrylBurke]

Please go through the Forum Rules, particularly the second paragraph.

I've closed the other thread you started. Moreover, as the question has nothing to do with AWT/Swing, I'm moving this one to New to Java.

db

[DarrylBurke]

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at leaveDataModel.StaffList.getObservers(StaffList.ja va:25)

So, what's on line 25 of StaffList.java?

db

[Schillers]

So, what's on line 25 of StaffList.java?

db

My apologies. To be honest, I'm that new to Java I thought that was swing...

Thank you for responding though!

    public ArrayList<IObserver> getObservers()
    {
        ArrayList<IObserver> arlResult = new ArrayList<>();
        for (IObserver currObserver : observers)                                 //THIS IS LINE 25
        {
            arlResult.add(currObserver);
        }
        return arlResult;
    }

[JosAH]

If the NPE exception was thrown on that line then 'observers' was null; b.t.w. if the intention of that method is to return a copy of the observers collection, you can shorten the method to:

return new ArrayList<IObserver>(observers);

kind regards,

Jos

[Schillers]

If the NPE exception was thrown on that line then 'observers' was null; b.t.w. if the intention of that method is to return a copy of the observers collection, you can shorten the method to:

return new ArrayList<IObserver>(observers);

kind regards,

Jos

Thank you for all your help guys, was me being an idiot and not adding the line...

staffMembers.registerObserver(this);

Thank you for all your help though!