This is caused by the basic fact that you have broken the paint chain.
Painting in AWT/Swing is made of a chain of method calls. If you neglect to maintain this chain, you start ending up with paint artifacts, in the form you are seeing.
The Graphics context is a shared resource, that is, every component painted during any given paint cycle will be given the same Graphics resource. Each component is expected to prepare the Graphics context before painting to it…
To fix the problem, in all your paint methods, you should be calling super.paint(g) to ensure that the paint chain is maintained and that the Graphics context is preapred for the individual components painting needs.
Having said that. It is not recommended to override paint of top level containers. Instead, it is recommended that you perform your custom painting using something like a JPanel and override it’s paintComponent method instead (ensuring that you call super.paintComponent as well!)
This has a least two basic benefits. The first is, you can know decide where the panel should be displayed, for example, you could add it to an JApplet or JFrame or other container as you see fit. It is double buffered by default. This means you won’t see any flicker when the painting is updated.
You should consider breaking your application down into small panels, focusing on each of the components needs separately. This will help reduce the complexity of your application and make it easier to manage the individual needs of each section of your application.
Take a look at Performing Custom Painting and Painting in AWT and Swing for more details
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