How to Change a JLabel in a Frame when a Button is clicked?

I have a JFrame object that has as a field:

ArrayList<JLabel> arrayFullOfLabels = new ArrayList<JLabel>();

I have a method:

void setArrayFullOfLabels()
{
for(int i=0;i<5;i++)
{
arrayFullOfLabels.add(new JLabel(arrayFullOfDiceImages.get(i)));
}
}

And in my constructor somewhere I call this setArrayFullOfLabels..

When I run my JFrame, I see the JLabes just fine..

I also have a button, When I click the button I want the JLabel to change..

mainFrame.arrayFullOfLabels.set(2, new JLabel("WHYYY!!!"));

But it is not working..

Any help?

( The actionListener is working just fine and I have mainFrame.validate() and mainFrame.repaint() )