in src/main/java/com/uber/h3core/H3Core.java [338:346]
public List<Long> gridRingUnsafe(long h3, int k) {
int sz = k == 0 ? 1 : 6 * k;
long[] out = new long[sz];
h3Api.gridRingUnsafe(h3, k, out);
return nonZeroLongArrayToList(out);
}