I would just comment on etahuin's answer, but I don't have a reputation yet.
Anyway, call this before creating the JSlider:
UIManager.put("Slider.paintValue", false);
"V" paintValue.
, , UIManager, UIManager:
Iterator<Entry<Object, Object>> it = UIManager.getDefaults().entrySet().iterator();
while(it.hasNext())
System.out.println(it.next());