For Java it is even easier as we have many tests 
See https://github.com/graphhopper/graphhopper/blob/master/web/src/test/java/com/graphhopper/http/resources/RouteResourceCustomModelLMTest.java
and https://github.com/graphhopper/graphhopper/blob/master/web/src/test/java/com/graphhopper/http/resources/RouteResourceCustomModelTest.java (see e.g. profile car_no_unclassified)
E.g. if you want to add a CH preparation for your car profile and the custom_veh profile in your code above you just append:
...
.setCHProfiles(Arrays.asList(new CHProfile("car"), new CHProfile("custom_veh")));