It is an .plist property
Look here:
file:///Developer/Documentation/Java/Reference/Java141SysProperties/System_Properties/index.html
The one of interest is apple.awt.brushMetalLook
Then you set it in your main function like this:
System.setProperty("apple.awt.showGrowBox", "true");
System.setProperty("apple.awt.antialiasing", "true");
System.setProperty("apple.awt.window.position.forc eSafeUserPositioning", "true");
System.setProperty("apple.awt.brushMetalLook", "true");
Or in the plist file when you package as a bundles. Play with it I got it working a while back.