Is it good to pass minimal parameters?

Question

Assume I have an object Car, with five parameters, { numwheels, color, mileage, horsepower, maxSpeed }. I have a method that needs 3 of these values. Which of the 2 options is said to be best practice ? Is it better to pass enclosing object and reduce the number of parameters, OR just pass in bare-minimal data to a method (eg: numwheels and color will not be accessed in method 2) ?

1. Option 1 pass whole object:

   void compute(Car c, Person p) {
       return c.mileage + c.horsepower + c.maxSpeed + p.age;
   }
   

2. Option 2: pass in just the method values.

   void compute(int mileage, int horsepower, int maxSpeed, int age) {
       return mileage + horsepower + maxSpeed + age.;
   }
   

Note: assume for some reason, compute cannot be a part of Car class. Please answer with that assumption in mind.

Answer 1

It's better to pass the enclosed object because any change in the number of parameters required in the computation wouldn't affect the method signature in future.

You can, in fact, accept an interface type, say, Vehicle instead. This allows the same method to compute data on Bike, Jet etc. later on.

public int compute(Vehicle veh) {
    return veh.computePerformance();
}

where Car implements the method as

public int computePerformance() {
    return mileage + horsepower + maxSpeed;
}

The idea is to write code that easily lends itself to extensibility.

Answer 2

I would suggest a third option: add a method "compute" to Car.

This is called "Tell, don't ask".

See http://martinfowler.com/bliki/TellDontAsk.html