SortedMap<String, Integer> subMap = map.subMap("a", "b");
    assertTrue(subMap instanceof SynchronizedSortedMap);
    assertSame(mutex, ((SynchronizedSortedMap<String, Integer>) subMap).mutex);
  }

  public void testSubMap_K_B_K_B() {
    NavigableMap<String, Integer> map = create();
    NavigableMap<String, Integer> subMap = map.subMap("a", true, "b", false);
    assertTrue(subMap instanceof SynchronizedNavigableMap);

    assertEquals(ImmutableMap.of("banana", 6, "dog", 3), filtered.headMap("emu"));

    assertEquals(ImmutableMap.of("banana", 6), filtered.subMap("banana", "dog"));
    assertEquals(ImmutableMap.of("dog", 3), filtered.subMap("cat", "emu"));

    assertEquals(ImmutableMap.of("dog", 3), filtered.tailMap("cat"));
    assertEquals(ImmutableMap.of("banana", 6, "dog", 3), filtered.tailMap("banana"));
  }

    }

    @Override
    public Entry<K, V>[] createArray(int length) {
      return delegate.createArray(length);
    }
  }

  /** Two bounds (from and to) define how to build a subMap. */
  public enum Bound {
    INCLUSIVE,
    EXCLUSIVE,
    NO_BOUND;
  }

  public static class SortedSetSubsetTestSetGenerator<E extends @Nullable Object>
      implements TestSortedSetGenerator<E> {

    holderA.value = 3;
    assertTrue(map.entrySet().contains(Maps.immutableEntry("a", new IntHolder(3))));
    Map<String, Integer> intMap = ImmutableSortedMap.of("a", 3, "b", 2);
    assertEquals(intMap.hashCode(), map.entrySet().hashCode());
    assertEquals(intMap.hashCode(), map.hashCode());
  }

  @J2ktIncompatible
  @GwtIncompatible // SerializableTester
  public void testViewSerialization() {

    public void clear() {
      standardClear();
    }

    @Override
    public boolean isEmpty() {
      return standardIsEmpty();
    }

    @Override
    public SortedMap<K, V> subMap(K fromKey, K toKey) {
      return standardSubMap(fromKey, toKey);
    }

    @Override
    public @Nullable Entry<K, V> lowerEntry(K key) {
      return standardLowerEntry(key);
    }

    @Override

    j.appendTo(sb2, ImmutableMultimap.of(1, 2, 3, 4, 5, 6, 1, 3, 5, 10).entries().iterator());
    assertEquals("1:2;1:3;3:4;5:6;5:10", sb2.toString());
  }

  public void test_skipNulls_onMap() {
    Joiner j = Joiner.on(",").skipNulls();
    try {
      j.withKeyValueSeparator("/");
      fail();
    } catch (UnsupportedOperationException expected) {
    }
  }

   * Compares strings in natural order except that null comes immediately before a given value. This
   * works better than Ordering.natural().nullsFirst() because, if null comes before all other
   * values, it lies outside the submap/submultiset ranges we test, and the variety of tests that
   * exercise null handling fail on those subcollections.
   */
  public abstract static class NullsBefore implements Comparator<@Nullable String>, Serializable {

    assertEquals(ImmutableMap.of("google", googleValues, "foo", fooValues), asMap.headMap("h"));
    assertEquals(ImmutableMap.of("google", googleValues), asMap.subMap("g", "h"));
  }

  public void testTailSetClear() {
    TreeMultimap<String, Integer> multimap = TreeMultimap.create();
    multimap.put("a", 1);
    multimap.put("a", 11);
    multimap.put("b", 2);

  }

  @Override
  public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
    return new SafeTreeMap<>(
        delegate.subMap(checkValid(fromKey), fromInclusive, checkValid(toKey), toInclusive));
  }

  @Override
  public SortedMap<K, V> subMap(K fromKey, K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override

  }

  @Override
  public NavigableMap<K, V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive) {
    return new SafeTreeMap<>(
        delegate.subMap(checkValid(fromKey), fromInclusive, checkValid(toKey), toInclusive));
  }

  @Override
  public SortedMap<K, V> subMap(K fromKey, K toKey) {
    return subMap(fromKey, true, toKey, false);
  }

  @Override