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I suppose it is a question of who paints last. If the layout of the components is done first, and the painting after, the painter will win. If the painter goes first then the layout will win.
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Either you paint on the frame or you layout components on the frame. Not both
Create a JPanel extension class, put your paintComponent method in that and add that to the frame.

What does the functions class do?
The code works for me when I comment out the functions line

Just recompiled and now it doesn't work the same way.

If I rename the paint method to paintXXX...