@Override public boolean equals(Object compareKey){
  return (compareKey instanceof MonKeyImp && summaryLabel.equals(((MonKeyImp)compareKey).summaryLabel) && units.equals(((MonKeyImp)compareKey).units));
}

@ Override public boolean equals ( Object compareKey ) { return ( compareKey instanceof MonKeyImp && summaryLabel . equals ( ( ( MonKeyImp ) compareKey ) . summaryLabel ) && units . equals ( ( ( MonKeyImp ) compareKey ) . units ) ) ; }
this method is called automatically by a hashmap when this class is used as a hashmap key . a coordinate is considered equal if its x and y variables have the same value .
