Java's Swing JSlider creates a sliding widget for selecting a number within a fixed range. The sliding "thumb" icon, the track it slides on, tick marks, and labels may be turned on and off, but Swing has no other methods to affect the appearance of a JSlider. That's left up to the current look and feel. This article shows how to use Apple's "Mac OS X" look and feel for Java on a Mac to create smaller JSliders and switch between two thumb icon styles. The article also shows work-arounds for controlling tick and label sizes and colors.
Windows automatically adds a window frame to all Java windows, but there is more that you can do to make sure Java windows look and feel right on Windows XP, Vista, 7, and beyond. This article discusses Swing settings to control the appearance of window decorations on a PC.