};

  private final NavigableSet<E> delegate;

  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 final NavigableSet<E> delegate;

  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));
  }

                        new SafeTreeSet<String>(Arrays.asList(elements)));
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .named("ForwardingNavigableSet[SafeTreeSet] with standard implementations")

            .named("SafeTreeSet with natural comparator")
            .createTestSuite());
    suite.addTest(
        SetTestSuiteBuilder.using(
                new TestStringSetGenerator() {
                  @Override
                  protected Set<String> create(String[] elements) {
                    NavigableSet<String> set = new SafeTreeSet<>(Ordering.natural().nullsFirst());

            .named("SafeTreeSet with natural comparator")
            .createTestSuite());
    suite.addTest(
        SetTestSuiteBuilder.using(
                new TestStringSetGenerator() {
                  @Override
                  protected Set<String> create(String[] elements) {
                    NavigableSet<String> set = new SafeTreeSet<>(Ordering.natural().nullsFirst());

                        new SafeTreeSet<String>(Arrays.asList(elements)));
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .named("ForwardingNavigableSet[SafeTreeSet] with standard implementations")

                        new SafeTreeSet<String>(Arrays.asList(elements)));
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .named("ForwardingSortedSet[SafeTreeSet] with standard implementations")

                        new SafeTreeSet<String>(Arrays.asList(elements)));
                  }

                  @Override
                  public List<String> order(List<String> insertionOrder) {
                    return Lists.newArrayList(Sets.newTreeSet(insertionOrder));
                  }
                })
            .named("ForwardingSortedSet[SafeTreeSet] with standard implementations")

import com.google.common.collect.Synchronized.SynchronizedSortedSet;
import com.google.common.collect.testing.NavigableSetTestSuiteBuilder;
import com.google.common.collect.testing.SafeTreeSet;
import com.google.common.collect.testing.TestStringSortedSetGenerator;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;

import com.google.common.collect.Synchronized.SynchronizedSortedSet;
import com.google.common.collect.testing.NavigableSetTestSuiteBuilder;
import com.google.common.collect.testing.SafeTreeSet;
import com.google.common.collect.testing.TestStringSortedSetGenerator;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;