Swing(jFrame) can not initialize

It is a known issue that macos with XstartOnFirstThread doesn’t play nicely with AWT and other graphical contexts mixed together. But if you are running that example in its own jvm instance, without a jme app running next to it, then it is pretty weird that it freezes. Anyway, my suggestion is to not use swing or awt at all, in jme you can use Lemur by jMonkeyEngine-Contributions that is pretty nice and integrates perfectly with the engine.