@Override
  public boolean equals(final Object obj) {
    if (this == obj) {
      return true;
    }
    if (obj == null) {
      return false;
    }
    if (getClass() != obj.getClass()) {
      return false;
    }
    final Digit other = (Digit) obj;
    if (m_digitValue != other.m_digitValue) {
      return false;
    }
    if (m_topMiddleBottom == null) {
      if (other.m_topMiddleBottom != null) {
        return false;
      }
    } else if (!m_topMiddleBottom.equals(other.m_topMiddleBottom)) {
      return false;
    }
    return true;
  }