* forward to this implementation.
   *
   * @since 7.0
   */
  protected String standardToString() {
    return Maps.toStringImpl(this);
  }

   * forward to this implementation.
   *
   * @since 7.0
   */
  protected String standardToString() {
    return Maps.toStringImpl(this);
  }

  public void testToStringImplWithNullEntries() throws Exception {
    List<@Nullable String> list = new ArrayList<>();
    list.add("foo");
    list.add(null);

    assertEquals(list.toString(), Collections2.toStringImpl(list));
  }

  public void testToStringImplWithNullEntries() throws Exception {
    List<@Nullable String> list = new ArrayList<>();
    list.add("foo");
    list.add(null);

    assertEquals(list.toString(), Collections2.toStringImpl(list));
  }

    for (Object o : c) {
      if (!self.contains(o)) {
        return false;
      }
    }
    return true;
  }

  /** An implementation of {@link Collection#toString()}. */
  static String toStringImpl(Collection<?> collection) {
    StringBuilder sb = newStringBuilderForCollection(collection.size()).append('[');
    boolean first = true;
    for (Object o : collection) {
      if (!first) {
        sb.append(", ");