*/
@GwtIncompatible // uses NavigableMap
public class TreeRangeSet<C extends Comparable<?>> extends AbstractRangeSet<C>
    implements Serializable {

  @VisibleForTesting final NavigableMap<Cut<C>, Range<C>> rangesByLowerBound;

  /** Creates an empty {@code TreeRangeSet} instance. */
  public static <C extends Comparable<?>> TreeRangeSet<C> create() {
    return new TreeRangeSet<>(new TreeMap<Cut<C>, Range<C>>());
  }

   *
   * <p>This is essentially the same as {@code
   * TreeRangeSet.create(this).removeAll(other.complement())} except it returns an {@code
   * ImmutableRangeSet}.
   *
   * @since 21.0
   */
  public ImmutableRangeSet<C> intersection(RangeSet<C> other) {
    RangeSet<C> copy = TreeRangeSet.create(this);
    copy.removeAll(other.complement());
    return copyOf(copy);
  }

  /**

 *
 * <p>Implementations that choose to support the {@link #add(Range)} operation are required to
 * ignore empty ranges and coalesce connected ranges. For example:
 *
 * {@snippet :
 * RangeSet<Integer> rangeSet = TreeRangeSet.create();
 * rangeSet.add(Range.closed(1, 10)); // {[1, 10]}
 * rangeSet.add(Range.closedOpen(11, 15)); // disconnected range; {[1, 10], [11, 15)}
 * rangeSet.add(Range.closedOpen(15, 20)); // connected range; {[1, 10], [11, 20)}

  }

  public enum RangeSetImpl {
    TreeRangeSetImpl {
      @Override
      <K extends Comparable<K>> RangeSet<K> create(RangeSet<K> contents) {
        return TreeRangeSet.create(contents);
      }
    },
    ImmutableRangeSetImpl {
      @Override
      <K extends Comparable<K>> RangeSet<K> create(RangeSet<K> contents) {
        return ImmutableRangeSet.copyOf(contents);