public SafeTreeSet() {
    this(new TreeSet<E>());
  }

  public SafeTreeSet(Collection<? extends E> collection) {
    this(new TreeSet<E>(collection));
  }

  public SafeTreeSet(Comparator<? super E> comparator) {
    this(new TreeSet<E>(comparator));
  }

  public SafeTreeSet(SortedSet<E> set) {
    this(new TreeSet<E>(set));
  }

  private SafeTreeSet(NavigableSet<E> delegate) {

    verifySetContents(set, EMPTY_COLLECTION);
  }

  public void testNewTreeSetEmpty() {
    TreeSet<Integer> set = Sets.newTreeSet();
    verifySortedSetContents(set, EMPTY_COLLECTION, null);
  }

  public void testNewTreeSetEmptyDerived() {
    TreeSet<Derived> set = Sets.newTreeSet();
    assertTrue(set.isEmpty());
    set.add(new Derived("foo"));
    set.add(new Derived("bar"));

    assertTrue(ArbitraryInstances.get(TreeSet.class).isEmpty());
    assertTrue(ArbitraryInstances.get(TreeMap.class).isEmpty());
    assertFreshInstanceReturned(
        LinkedList.class,
        Deque.class,
        Queue.class,
        PriorityQueue.class,
        BitSet.class,
        TreeSet.class,
        TreeMap.class);
  }

  public void testGet_misc() {

    return generateTreeSet(freshElement);
  }

  @Generates
  static <E extends Comparable<? super E>> TreeSet<E> generateTreeSet(E freshElement) {
    TreeSet<E> set = Sets.newTreeSet();
    set.add(freshElement);
    return set;
  }

  @Generates
  static <E extends Comparable<? super E>> ImmutableSortedSet<E> generateImmutableSortedSet(

            new TestStringSortedSetGenerator() {
              @Override
              public SortedSet<String> create(String[] elements) {
                return new TreeSet<>(MinimalCollection.of(elements));
              }
            })
        .named("TreeSet, natural")
        .withFeatures(
            SetFeature.GENERAL_PURPOSE,
            CollectionFeature.SERIALIZABLE,
            CollectionFeature.KNOWN_ORDER,

   * use the {@code TreeSet} constructor directly, taking advantage of <a
   * href="http://goo.gl/iz2Wi">"diamond" syntax</a>.
   *
   * @return a new, empty {@code TreeSet}
   */
  @SuppressWarnings("rawtypes") // https://github.com/google/guava/issues/989
  public static <E extends Comparable> TreeSet<E> newTreeSet() {
    return new TreeSet<>();
  }

  /**

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NavigableSet;
import java.util.TreeSet;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests operations on a NavigableSet. Can't be invoked directly; please
 * see {@code NavigableSetTestSuiteBuilder}.
 *
 * @author Jesse Wilson

    return generateTreeSet(freshElement);
  }

  @Generates
  static <E extends Comparable<? super E>> TreeSet<E> generateTreeSet(E freshElement) {
    TreeSet<E> set = Sets.newTreeSet();
    set.add(freshElement);
    return set;
  }

  @Generates
  static <E extends Comparable<? super E>> ImmutableSortedSet<E> generateImmutableSortedSet(

  private static <E extends Comparable<? super E>> SortedSet<E> nullCheckedTreeSet(E[] elements) {
    SortedSet<E> set = newTreeSet();
    for (E element : elements) {
      // Explicit null check because TreeSet wrongly accepts add(null) when empty.
      set.add(checkNotNull(element));
    }
    return set;
  }

  public static class ContiguousSetGenerator extends AbstractContiguousSetGenerator {
    @Override

  }

  /**
   * {@inheritDoc}
   *
   * <p>Creates an empty {@code TreeSet} for a collection of values for one key.
   *
   * @return a new {@code TreeSet} containing a collection of values for one key
   */
  @Override
  SortedSet<V> createCollection() {
    return new TreeSet<>(valueComparator);
  }

  @Override
  Collection<V> createCollection(@ParametricNullness K key) {