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

  static class SameShortInstance {
    private final Short i;

    public SameShortInstance(Short i) {
      this.i = checkNotNull(i);
    }