List<String> list = Lists.newArrayList(elements);
      list.add("\0");
      list.add("zzz");
      return ImmutableSortedSet.copyOf(list).subSet("\0\0", "zzy");
    }
  }

  @GwtIncompatible // NavigableSet
  public static class ImmutableSortedSetDescendingGenerator extends TestStringSortedSetGenerator {
    @Override
    protected SortedSet<String> create(String[] elements) {

import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link NavigableSet} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *

  class WrappedNavigableSet extends WrappedSortedSet implements NavigableSet<V> {
    WrappedNavigableSet(
        @ParametricNullness K key,
        NavigableSet<V> delegate,
        @CheckForNull WrappedCollection ancestor) {
      super(key, delegate, ancestor);
    }

    @Override
    NavigableSet<V> getSortedSetDelegate() {
      return (NavigableSet<V>) super.getSortedSetDelegate();
    }

    @Override

   * {@code null} if this multiset is empty.
   */
  @CheckForNull
  Entry<E> pollLastEntry();

  /**
   * Returns a {@link NavigableSet} view of the distinct elements in this multiset.
   *
   * @since 14.0 (present with return type {@code SortedSet} since 11.0)
   */
  @Override
  NavigableSet<E> elementSet();

  /**
   * {@inheritDoc}
   *

    @Override
    public NavigableMap<K, V> descendingMap() {
      return new StandardDescendingMap();
    }

    @Override
    public NavigableSet<K> navigableKeySet() {
      return new StandardNavigableKeySet();
    }

    @Override
    public NavigableSet<K> descendingKeySet() {
      return standardDescendingKeySet();
    }

    @Override
    public K firstKey() {
      return standardFirstKey();

    suite.addTest(
        NavigableSetTestSuiteBuilder.using(
                new TestStringSetGenerator() {
                  @Override
                  public NavigableSet<String> create(String[] elements) {
                    NavigableSet<String> unfiltered = Sets.newTreeSet();
                    unfiltered.add("yyy");
                    unfiltered.addAll(ImmutableList.copyOf(elements));

  @Override
  int indexOf(@CheckForNull Object target) {
    return -1;
  }

  @Override
  public UnmodifiableIterator<C> iterator() {
    return Iterators.emptyIterator();
  }

  @GwtIncompatible // NavigableSet
  @Override
  public UnmodifiableIterator<C> descendingIterator() {
    return Iterators.emptyIterator();
  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override

  }

  AbstractSortedMultiset(Comparator<? super E> comparator) {
    this.comparator = checkNotNull(comparator);
  }

  @Override
  public NavigableSet<E> elementSet() {
    return (NavigableSet<E>) super.elementSet();
  }

  @Override
  NavigableSet<E> createElementSet() {
    return new SortedMultisets.NavigableElementSet<>(this);
  }

  @Override
  public Comparator<? super E> comparator() {

import com.google.common.testing.SerializableTester;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.NavigableSet;
import java.util.Set;
import java.util.SortedSet;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;

public class SafeTreeSetTest extends TestCase {

import com.google.common.testing.SerializableTester;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.NavigableSet;
import java.util.Set;
import java.util.SortedSet;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;

public class SafeTreeSetTest extends TestCase {