Object outputstream, cant write object with properties to file

[Parashurama]

Hi,
I searched through the forum, but could not find an answer to my question so Ill ask in this post.

What I want to do is writing an object to a file.
My issue is that It only works if the Object is "empty"
I have a class called Mob, which have a name property (String).
If I try to write the object to file without setting the name property I get a file and no errors, but if I set the name property I get loads of errors.

See below for erroes and code:

Code :
Mob Class:

public class Mob {
    // Variables
    String name;
    
}

My button code:

private void btnSaveActionPerformed(java.awt.event.ActionEvent evt) {
        mobTemp.name = txtMobName.getText();
        try {
            // write mobTemp to a file
            writeTemp();
        } catch (IOException ex) {
            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(MainWindow.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

I had to create a writeTemp method cause I could not add "throws IOException, ClassNotFoundException" to my Netbeans generated button code "header"

writeTemp method:

public void writeTemp() throws IOException, ClassNotFoundException{
        FileOutputStream fos = new FileOutputStream("file.dat");
	ObjectOutputStream oos = new ObjectOutputStream(fos);
        oos.writeObject(mobTemp);
	oos.close();
    }

My button code fails if I have
mobTemp.name = txtMobName.getText();
but does not fail if I remove it. Then it makes the file.dat file.

I hope this was understandable. Please let me know if more info is needed.

Parashurama

[Tolls]

Without the full exception (plus stacktrace) we can't say.

[Parashurama]

Sorry, I ment to write down the errors as well.

Here they are:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at MUD.MainWindow.btnSaveActionPerformed(MainWindow.java:249)   "This corresponds to line 2 in my button code"
	at MUD.MainWindow.access$000(MainWindow.java:18)
	at MUD.MainWindow$1.actionPerformed(MainWindow.java:166)
	at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
	at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
	at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
	at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
	at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
	at java.awt.Component.processMouseEvent(Component.java:6505)
	at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
	at java.awt.Component.processEvent(Component.java:6270)
	at java.awt.Container.processEvent(Container.java:2229)
	at java.awt.Component.dispatchEventImpl(Component.java:4861)
	at java.awt.Container.dispatchEventImpl(Container.java:2287)
	at java.awt.Component.dispatchEvent(Component.java:4687)
	at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
	at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
	at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
	at java.awt.Container.dispatchEventImpl(Container.java:2273)
	at java.awt.Window.dispatchEventImpl(Window.java:2719)
	at java.awt.Component.dispatchEvent(Component.java:4687)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:703)
	at java.awt.EventQueue.access$000(EventQueue.java:102)
	at java.awt.EventQueue$3.run(EventQueue.java:662)
	at java.awt.EventQueue$3.run(EventQueue.java:660)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.awt.EventQueue$4.run(EventQueue.java:676)
	at java.awt.EventQueue$4.run(EventQueue.java:674)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:673)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)

[Tolls]

txtMobName is null.
As to why (other than it not being initialised) I can't say.

[Parashurama]

Yes, that was it.
I never initialised the object, just declared it.

Thanks for your help!