return create(Range.closedOpen(lower, upper), DiscreteDomain.longs());
  }

  final DiscreteDomain<C> domain;

  ContiguousSet(DiscreteDomain<C> domain) {
    super(Ordering.natural());
    this.domain = domain;
  }

  @Override
  public ContiguousSet<C> headSet(C toElement) {
    return headSetImpl(checkNotNull(toElement), false);
  }

  /**
   * @since 12.0

   * computation is {@linkplain java.util.concurrent.Future#isDone() complete} or, if the
   * computation is already complete, immediately.
   *
   * <p>The callback is run on {@code executor}. There is no guaranteed ordering of execution of
   * callbacks, but any callback added through this method is guaranteed to be called once the
   * computation is complete.
   *

import org.dbflute.cbean.coption.StatementConfigCall;
import org.dbflute.cbean.dream.SpecifiedColumn;
import org.dbflute.cbean.exception.ConditionBeanExceptionThrower;
import org.dbflute.cbean.ordering.OrderByBean;
import org.dbflute.cbean.paging.PagingBean;
import org.dbflute.cbean.paging.PagingInvoker;
import org.dbflute.cbean.scoping.AndQuery;
import org.dbflute.cbean.scoping.ModeQuery;

import org.dbflute.cbean.coption.StatementConfigCall;
import org.dbflute.cbean.dream.SpecifiedColumn;
import org.dbflute.cbean.exception.ConditionBeanExceptionThrower;
import org.dbflute.cbean.ordering.OrderByBean;
import org.dbflute.cbean.paging.PagingBean;
import org.dbflute.cbean.paging.PagingInvoker;
import org.dbflute.cbean.scoping.AndQuery;
import org.dbflute.cbean.scoping.ModeQuery;

  @Override
  protected <K, V> NavigableMap<K, V> create() {
    @SuppressWarnings("unchecked")
    NavigableMap<K, V> innermost =
        new SafeTreeMap<>((Comparator<? super K>) Ordering.natural().nullsFirst());
    TestMap<K, V> inner = new TestMap<>(innermost, mutex);
    NavigableMap<K, V> outer = Synchronized.navigableMap(inner, mutex);
    return outer;
  }

@SuppressWarnings({"serial", "rawtypes"})
final class RegularImmutableSortedSet<E> extends ImmutableSortedSet<E> {
  static final RegularImmutableSortedSet<Comparable> NATURAL_EMPTY_SET =
      new RegularImmutableSortedSet<>(ImmutableList.of(), Ordering.natural());

  private final transient ImmutableList<E> elements;

  RegularImmutableSortedSet(ImmutableList<E> elements, Comparator<? super E> comparator) {
    super(comparator);
    this.elements = elements;
  }

 *
 * {@snippet :
 * public int compareTo(Foo that) {
 *   return ComparisonChain.start()
 *       .compare(this.aString, that.aString)
 *       .compare(this.anInt, that.anInt)
 *       .compare(this.anEnum, that.anEnum, Ordering.natural().nullsLast())
 *       .result();
 * }
 * }
 *
 * <p>The value of this expression will have the same sign as the <i>first nonzero</i> comparison

    return create(Range.closedOpen(lower, upper), DiscreteDomain.longs());
  }

  final DiscreteDomain<C> domain;

  ContiguousSet(DiscreteDomain<C> domain) {
    super(Ordering.natural());
    this.domain = domain;
  }

  @Override
  public ContiguousSet<C> headSet(C toElement) {
    return headSetImpl(checkNotNull(toElement), false);
  }

  /**
   * @since 12.0

 *
 * {@snippet :
 * public int compareTo(Foo that) {
 *   return ComparisonChain.start()
 *       .compare(this.aString, that.aString)
 *       .compare(this.anInt, that.anInt)
 *       .compare(this.anEnum, that.anEnum, Ordering.natural().nullsLast())
 *       .result();
 * }
 * }
 *
 * <p>The value of this expression will have the same sign as the <i>first nonzero</i> comparison

        new SynchronousQueue<Object>(),
        new ArrayBlockingQueue<Object>(10),
        new LinkedBlockingDeque<Object>(),
        new LinkedBlockingDeque<Object>(10),
        new PriorityBlockingQueue<Object>(10, Ordering.arbitrary()));
  }

  /*
   * We need to perform operations in a thread pool, even for simple cases, because the queue might
   * be a SynchronousQueue.
   */
  private ExecutorService threadPool;