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

  static class SameDoubleInstance {
    private final Double i;

    public SameDoubleInstance(Double i) {
      this.i = checkNotNull(i);
    }