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) {

  }

  /**
   * {@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) {

 * Collections#singleton(Object)} and {@link java.util.LinkedHashSet} for empty, singleton and
 * regular sets respectively. For the sorted sets, it's a thin wrapper around {@link
 * java.util.TreeSet}.
 *
 * @see ImmutableSortedSet
 * @author Hayward Chan
 */
@ElementTypesAreNonnullByDefault
@SuppressWarnings("serial") // Serialization only done in GWT.

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 Helpers.getMethod(CollectionAddTester.class, "testAdd_nullSupported");
  }

  /**
   * Returns the {@link Method} instance for {@link #testAdd_nullSupported()} so that tests of
   * {@link java.util.TreeSet} can suppress it with {@code
   * FeatureSpecificTestSuiteBuilder.suppressing()} until <a
   * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5045147">Sun bug 5045147</a> is fixed.
   */
  @J2ktIncompatible

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

  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) {

import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.TreeSet;
import junit.framework.TestCase;
import junit.framework.TestSuite;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@link Sets#synchronizedNavigableSet(NavigableSet)}.
 *

import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.TreeSet;
import junit.framework.TestCase;
import junit.framework.TestSuite;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@link Sets#synchronizedNavigableSet(NavigableSet)}.
 *

    return Helpers.getMethod(CollectionAddTester.class, "testAdd_nullSupported");
  }

  /**
   * Returns the {@link Method} instance for {@link #testAdd_nullSupported()} so that tests of
   * {@link java.util.TreeSet} can suppress it with {@code
   * FeatureSpecificTestSuiteBuilder.suppressing()} until <a
   * href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5045147">Sun bug 5045147</a> is fixed.
   */
  @J2ktIncompatible