private boolean check( String s1, String s2)
  {
    boolean b1 = true ;  // s1 = empty

    if (s1 != null)   // check, if s1 contains some data
    {
      if (s1.length() > 0)
      {
        b1 = false ;
      }
    }

    boolean b2 = true ;  // s2 = empty

    if (s2 != null)   // check, if s1 contains some data
    {
      if (s2.length() > 0)
      {
        b2 = false ;
      }
    }

    if (b1 || b2)  // one is empty
    {
      // if s1 & s2 are empty => definition is equal....
      if ( b1 && b2 )
      {
        return true ;
      }
      return false ;
    }

    // different ?
    if (s1.toLowerCase().hashCode() != s2.toLowerCase().hashCode())
    {
      return false ;
    }

    return true ;
  }