return Iterators.pollNext(descendingMap().entrySet().iterator());
  }

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

  /**
   * A sensible implementation of {@link NavigableMap#descendingMap} in terms of the methods of this
   * {@code NavigableMap}. In many cases, you may wish to override {@link

    return Iterators.pollNext(descendingMap().entrySet().iterator());
  }

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

  /**
   * A sensible implementation of {@link NavigableMap#descendingMap} in terms of the methods of this
   * {@code NavigableMap}. In many cases, you may wish to override {@link

  protected SortedMap<String, Integer> makePopulatedMap() {
    NavigableMap<String, Integer> map = new SafeTreeMap<>();
    map.put("one", 1);
    map.put("two", 2);
    map.put("three", 3);
    return SerializableTester.reserialize(map);
  }

  @Override
  protected SortedMap<String, Integer> makeEmptyMap() throws UnsupportedOperationException {
    NavigableMap<String, Integer> map = new SafeTreeMap<>();

@GwtIncompatible
public final class SafeTreeMap<K, V> implements Serializable, NavigableMap<K, V> {
  @SuppressWarnings("unchecked")
  private static final Comparator<Object> NATURAL_ORDER =
      new Comparator<Object>() {
        @Override
        public int compare(Object o1, Object o2) {
          return ((Comparable<Object>) o1).compareTo(o2);
        }
      };

  private final NavigableMap<K, V> delegate;

  public SafeTreeMap() {

  protected SortedMap<String, Integer> makePopulatedMap() {
    NavigableMap<String, Integer> map = new SafeTreeMap<>();
    map.put("one", 1);
    map.put("two", 2);
    map.put("three", 3);
    return SerializableTester.reserialize(map);
  }

  @Override
  protected SortedMap<String, Integer> makeEmptyMap() throws UnsupportedOperationException {
    NavigableMap<String, Integer> map = new SafeTreeMap<>();

import java.util.Iterator;
import java.util.NavigableMap;
import java.util.NavigableSet;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedMap;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Skeletal implementation of {@link NavigableMap}.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible

@GwtIncompatible
public final class SafeTreeMap<K, V> implements Serializable, NavigableMap<K, V> {
  @SuppressWarnings("unchecked")
  private static final Comparator<Object> NATURAL_ORDER =
      new Comparator<Object>() {
        @Override
        public int compare(Object o1, Object o2) {
          return ((Comparable<Object>) o1).compareTo(o2);
        }
      };

  private final NavigableMap<K, V> delegate;

  public SafeTreeMap() {

        TestSortedMapGenerator<K, V> delegate, Bound to, Bound from) {
      super(delegate, to, from);
    }

    @Override
    NavigableMap<K, V> createSubMap(SortedMap<K, V> sortedMap, K firstExclusive, K lastExclusive) {
      NavigableMap<K, V> map = (NavigableMap<K, V>) sortedMap;
      if (from == Bound.NO_BOUND && to == Bound.INCLUSIVE) {
        return map.headMap(lastInclusive, true);

        @Override
        public CacheVersion apply(Map.Entry<GradleVersion, CacheVersion> input) {
            return input.getValue();
        }
    };

    private final NavigableMap<GradleVersion, CacheVersion> versions;

    private CacheVersionMapping(NavigableMap<GradleVersion, CacheVersion> versions) {
        Preconditions.checkArgument(!versions.isEmpty(), "versions must not be empty");
        this.versions = new TreeMap<>(versions);
    }

   * @since 12.0
   */
  @GwtIncompatible // NavigableMap
  public static <K extends @Nullable Object, V extends @Nullable Object>
      NavigableMap<K, V> unmodifiableNavigableMap(NavigableMap<K, ? extends V> map) {
    checkNotNull(map);
    if (map instanceof UnmodifiableNavigableMap) {
      @SuppressWarnings("unchecked") // covariant
      NavigableMap<K, V> result = (NavigableMap<K, V>) map;
      return result;
    } else {