Question

http://pastie.org/4372510 – Click this link for the code. (Didnt post it here to keep question clean)

I was recently trying to create a simple Java program in order to learn cardLayout.
I wanted this program to show a JLabel saying “Label1” in the beginning.
When the user clicks the label, I wanted to switch cards. i.e show Label2.

"Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at potpie.changeLabel(potpie.java:34)"

This is the error that I am getting. It says something is wrong with the line 50 in the code I have pasted.

I cant seem to figure out what is wrong.

Answer 1

    public void mouseClicked(MouseEvent arg0) 
    {
        potpie ccObj = new potpie();
        ccObj.changeLabel();
    }

Is calling changeLabel on a new potpie (I hate your class names and method names, by the way, they are meaningless), not on the one that was instantiated (with a call to .koko) in main.