Here is debugging swing Debugging Swing applications using the UI debugger , it can be very useful to debug the Swing related application.
Another Visual Debugger provided by NetBeans.
swinginspector is a Java Swing / AWT user interface analysis and debugging tool, functions and similar firebug, a powerful Swing / AWT user analysis and debugging user interface.
Here is another thing I found
When your JFrame is visible, press CTRL + SHIFT + F1 and look at the output console for the hierarchy of the tree of components and layouts.
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