question: @ Override public double calculateDistance ( double [ ] x1 , double [ ] x2 ) { double prod = a * innerProduct ( x1 , x2 ) + b ; double e1 = Math . exp ( prod ) ; double e2 = Math . exp ( - prod ) ; return ( ( e1 - e2 ) / ( e1 + e2 ) ) ; }
target:  Subclasses must implement this method. 