Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException !! $ !!

I am getting the following exception when I am running my Swing
Application. But the program continues and does not terminate abruptly
unlike general Exceptions

Exception in thread
"AWT-EventQueue-0" java.lang.NullPointerException
at
javax.swing.plaf.basic.BasicTreeUI.paintRow(BasicTreeUI.java:1399) />at
javax.swing.plaf.basic.BasicTreeUI.paint(BasicTreeUI.java:1189) />at javax.swing.plaf.ComponentUI.update(ComponentUI.java:142)
at
javax.swing.JComponent.paintComponent(JComponent.java:742)
at
javax.swing.JComponent.paint(JComponent.java:1005)
at
javax.swing.JComponent.paintWithOffscreenBuffer(JComponent.java:4963) />at javax.swing.JComponent.pai

I made a poker game and when I run it I get these errors...

run:
Exception in thread "AWT-EventQueue-0"
java.lang.NullPointerException
at
com.sun.java.swing.plaf.nimbus.NimbusStyle.init(NimbusStyle.java:418) />at
com.sun.java.swing.plaf.nimbus.NimbusStyle.validate(NimbusStyle.java:359) />at
com.sun.java.swing.plaf.nimbus.NimbusStyle.getValues(NimbusStyle.java:927) />at
com.sun.java.swing.plaf.nimbus.NimbusStyle.getInsets(NimbusStyle.java:605) />at
javax.swing.plaf.synth.SynthStyle.installDefaults(SynthStyle.java:896) />at
javax.swing.plaf.synth.SynthLookAndFeel.updateStyle(SynthLookAndFeel.java:275) />at
javax.swing.plaf.synth.SynthLabelUI.updateStyle(SynthLabelUI.java:53) />at javax.swing.plaf.synth.SynthLa

I am creating a GUI program with java and when I run it, I get this
stack of errors.

I have spent over a WEEK trying to figure out why my code isn't
working. It's a long code, I will post it all but I will break down
the code as I explain.
First off, I have called double[] arrays
and then initialized them later on in the program on certain steps.
What problem is that even though they are initialized, later on in the
code, it's telling me that the double[] I'm requesting is NULL, as if
it didn't know that I have already done all that and added elements to
it. Here's the program.....

Hi
I am using netbeans and mysql. I am trying to run the an
inventory system. I have linked the program with mysql. The program
is running but when in log in page I input username and password which
is preinstalled in mysql and then press submit, its not going to next
page but giving this error on netbeans: