android/guava/src/com/google/common/collect/Range.java
public static <C extends Comparable<?>> Range<C> singleton(C value) {
    return closed(value, value);
  }
public static <C extends Comparable<?>> Range<C> singleton(C value) {
    return closed(value, value);
  }
Returns a range that {@linkplain Range#contains(Comparable) contains} only the given value. The
returned range is {@linkplain BoundType#CLOSED closed} on both ends.

@since 14.0