Use static method inside instance method of the same class

Question

Let's say I have a class Point. I want to give the user the tool to easily calculate the distance between 2 Points, so I write the method:

static float distance (Point p1, Point p2)

Now, I also want to give the user the tool to directly calculate the distance between one Point he already instanciated and another Point:

float distance (Point p)

Is it a good idea to use the static method distance(Point, Point) inside the instance method distance(Point)? Something like:

float distance (Point p){
    return Point.distance(this, p);
}

This way I would reuse the code.

If it is a bad thing to do, why should I avoid this?

Answer 1

Many people have debated about the general pros and cons of static methods with regard to testability, much of it I agree with. So I am not going to elaborate on that but just answer your question:

• Avoiding code duplication is a good idea, do it.
• I would do it just the other way around and call p1.distance(p2) from the static utility method and put the calculation logic into the non-static method if you insist in keeping the static method (I would eliminate it). I would say there is good reason to ask "hey, I have got this point p1, give me its distance to p2". I fail to see how this gets any easier with a static method. You need to provide two Point instances anyway, there is nothing you can do without instances, so why make it static in the first place?