in src/main/java/org/apache/sling/feature/launcher/impl/launchers/AbstractRunner.java [410:418]
private static Iterable<Integer> sortStartLevels(final Collection<Integer> startLevels, final int defaultStartLevel) {
final List<Integer> result = new ArrayList<>(startLevels);
Collections.sort(result, (o1, o2) -> {
int i1 = o1 == 0 ? defaultStartLevel : o1;
int i2 = o2 == 0 ? defaultStartLevel : o2;
return Integer.compare(i1, i2);
});
return result;
}