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

  static class SameLongInstance {
    private final Long i;

    public SameLongInstance(Long i) {
      this.i = checkNotNull(i);
    }