android/guava/src/com/google/common/collect/ImmutableSortedMap.java
public static <K, V> Builder<K, V> orderedBy(Comparator<K> comparator) {
    return new Builder<>(comparator);
  }
public static <K, V> Builder<K, V> orderedBy(Comparator<K> comparator) {
    return new Builder<>(comparator);
  }
Returns a builder that creates immutable sorted maps with an explicit comparator. If the
comparator has a more general type than the map's keys, such as creating a {@code
SortedMap<Integer, String>} with a {@code Comparator<Number>}, use the {@link Builder}
constructor instead.

@throws NullPointerException if {@code comparator} is null