/**
  * The method checks if this Square and specified object (Square) are equal.
  *
  * @param obj - specified object.
  * @return boolean true if this Square is equal to specified object and false otherwise.
  */
 public boolean equals(final Object obj) {
   if (obj instanceof Square) {
     final Square square = (Square) obj;
     return rank.equals(square.rank);
   }
   return false;
 }