public boolean equals(@Nullable Object obj) {
      if (obj instanceof SameInterfaceInstance) {
        SameInterfaceInstance that = (SameInterfaceInstance) obj;
        return s == that.s;
      }
      return false;
    }
  }

  static class SameListInstance {
    private final List<?> s;

    public SameListInstance(List<?> s) {
      this.s = checkNotNull(s);
    }

    @Override