I think that this exception in Timer will never be thrown:
if(DisplaySystem.getSystemProvider() == null) {
throw new JmeException("Display System must be initialized before Timer.");
}
since getSystemProvider() in DisplaySystem will never return null:
public static SystemProvider getSystemProvider() {
SystemProvider currentProvider = system;
if (currentProvider != null) {
return currentProvider;
}
// if none defined by Service.providers, use fallback default
synchronized (DisplaySystem.class) {
if (system == null) {
system = new LWJGLSystemProvider();
}
return system;
}
}