Java Swing easy to use loading component to see the rendering download and execute LoadingSwingDemo.jar in the root of the repository.

We instanciate one of subclasses of LoadingPercentage class:
LoadingPie loading=new LoadingPie();

We can change the looking of the loading component through various methods

loading.setBackgroundSketchColor(Color.WHITE);
loading.setFillingColor(Color.RED);
loading.setTextColor(Color.BLACK);

add the loading component to any Swing Container:
panel.add(loading);

Set the loading percentage depending on your background processing, with
loading.setPosition(n) //n have to be an integer between 0 and 100