public double distance(Instance first, Instance second) {
    return distance(first, second, Double.POSITIVE_INFINITY);
  }
public double distance ( Instance first , Instance second ) { return distance ( first , second , Double . POSITIVE_INFINITY ) ; }
Calculates the distance between two instances.

@param first 	the first instance
@param second 	the second instance
@return 		the distance between the two given instances