code: @Nullable
    public DATATYPE getIfSuccess (@Nullable final DATATYPE aFailureValue)
    {
      return m_eSuccess.isSuccess () ? m_aObj : aFailureValue;
    }
docs: Get the store value if this is a success. Otherwise the passed failure
  value is returned.
  
  @param aFailureValue
  The failure value to be used. May be <code>null</code>.
  @return Either the stored value or the failure value. May be
  <code>null</code>.