java - UIManager.put() not working? -

i'm using app jsliders , setting , feel platform default. i'm trying set slider's thumb size using code:

uimanager.put("slider.thumbheight",5); uimanager.put("slider.thumbwidth",20); 

but size remains unchanged. i've tried this:

uimanager.getdefaults().put("slider.thumbheight",5); uimanager.getdefaults().put("slider.thumbwidth",20); 

same result, thumb on slider remains default size. i've calling before/after setting style there no difference.