android/guava/src/com/google/common/collect/Sets.java
@Beta
  @GwtIncompatible // NavigableSet
  public static <K extends Comparable<? super K>> NavigableSet<K> subSet(
      NavigableSet<K> set, Range<K> range) {
    if (set.comparator() != null
        && set.comparator() != Ordering.natural()
        && range.hasLowerBound()
        && range.hasUpperBound()) {
      checkArgument(
          set.comparator().compare(range.lowerEndpoint(), range.upperEndpoint()) <= 0,
          "set is using a custom comparator which is inconsistent with the natural ordering.");
    }
    if (range.hasLowerBound() && range.hasUpperBound()) {
      return set.subSet(
          range.lowerEndpoint(),
          range.lowerBoundType() == BoundType.CLOSED,
          range.upperEndpoint(),
          range.upperBoundType() == BoundType.CLOSED);
    } else if (range.hasLowerBound()) {
      return set.tailSet(range.lowerEndpoint(), range.lowerBoundType() == BoundType.CLOSED);
    } else if (range.hasUpperBound()) {
      return set.headSet(range.upperEndpoint(), range.upperBoundType() == BoundType.CLOSED);
    }
    return checkNotNull(set);
  }
@Beta
  @GwtIncompatible // NavigableSet
  public static <K extends Comparable<? super K>> NavigableSet<K> subSet(
      NavigableSet<K> set, Range<K> range) {
    if (set.comparator() != null
        && set.comparator() != Ordering.natural()
        && range.hasLowerBound()
        && range.hasUpperBound()) {
      checkArgument(
          set.comparator().compare(range.lowerEndpoint(), range.upperEndpoint()) <= 0,
          "set is using a custom comparator which is inconsistent with the natural ordering.");
    }
    if (range.hasLowerBound() && range.hasUpperBound()) {
      return set.subSet(
          range.lowerEndpoint(),
          range.lowerBoundType() == BoundType.CLOSED,
          range.upperEndpoint(),
          range.upperBoundType() == BoundType.CLOSED);
    } else if (range.hasLowerBound()) {
      return set.tailSet(range.lowerEndpoint(), range.lowerBoundType() == BoundType.CLOSED);
    } else if (range.hasUpperBound()) {
      return set.headSet(range.upperEndpoint(), range.upperBoundType() == BoundType.CLOSED);
    }
    return checkNotNull(set);
  }
@ Beta @ GwtIncompatible // NavigableSet public static < K extends Comparable < ? super K > > NavigableSet < K > subSet ( NavigableSet < K > set , Range < K > range ) { if ( set . comparator ( ) != null && set . comparator ( ) != Ordering . natural ( ) && range . hasLowerBound ( ) && range . hasUpperBound ( ) ) { checkArgument ( set . comparator ( ) . compare ( range . lowerEndpoint ( ) , range . upperEndpoint ( ) ) <= 0 , "set is using a custom comparator which is inconsistent with the natural ordering." ) ; } if ( range . hasLowerBound ( ) && range . hasUpperBound ( ) ) { return set . subSet ( range . lowerEndpoint ( ) , range . lowerBoundType ( ) == BoundType . CLOSED , range . upperEndpoint ( ) , range . upperBoundType ( ) == BoundType . CLOSED ) ; } else if ( range . hasLowerBound ( ) ) { return set . tailSet ( range . lowerEndpoint ( ) , range . lowerBoundType ( ) == BoundType . CLOSED ) ; } else if ( range . hasUpperBound ( ) ) { return set . headSet ( range . upperEndpoint ( ) , range . upperBoundType ( ) == BoundType . CLOSED ) ; } return checkNotNull ( set ) ; }
Returns a view of the portion of {@code set} whose elements are contained by {@code range}.

<p>This method delegates to the appropriate methods of {@link NavigableSet} (namely {@link
NavigableSet#subSet(Object, boolean, Object, boolean) subSet()}, {@link
NavigableSet#tailSet(Object, boolean) tailSet()}, and {@link NavigableSet#headSet(Object,
boolean) headSet()}) to actually construct the view. Consult these methods for a full
description of the returned view's behavior.

<p><b>Warning:</b> {@code Range}s always represent a range of values using the values' natural
ordering. {@code NavigableSet} on the other hand can specify a custom ordering via a {@link
Comparator}, which can violate the natural ordering. Using this method (or in general using
{@code Range}) with unnaturally-ordered sets can lead to unexpected and undefined behavior.

@since 20.0
Returns a view of the portion of { @code set } whose elements are contained by { @code range } .