Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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When I first learned about interfaces, by about this point in the discussion I got kind of
annoyed. I was able to follow how to code interfaces, but I didn’t get the benefit. I mean,
if you are forced to implement all the methods in the interface, why not just add the
methods directly to the class to begin with? Wouldn’t this be less work and less confusing?
What is the interface really giving you for this added effort? I think in retrospect that this
was a good question. At this point, there is not much apparent benefit.
Let’s now create another class that also implements the SportsGear interface, to see if you
can begin to see the power of interfaces. (This code is not intended to be run either—I’ll
get to that shortly.)
class Skis implements SportsGear{
//instance variables
String brandName;
float unitCost;
// constructor
Skis(String brandName, float unitCost){
this.brandName = brandName;
this.unitCost = unitCost;
}
// required implemented interface methods
String getBrandName(){
return brandName;
}
float getUnitCost(){
return unitCost;
}
void setUnitCost(float unitCost){
this.unitCost = unitCost;
}
void printWarranty(){
println("Skis: full replacement value for 5 years");
}
}
In the Skis class, you can see that I included the same method definitions as in the
Bicycle class. Notice also that I implemented the printWarranty() method a little differently
in each of the two classes. I have the freedom to do this because the interface
methods are empty. This is one of the benefits of using interfaces. They provide a shared
interface for communicating with a group of related classes, but still allow a customized
implementation of each of the common methods. As you get more experienced with
coding, you’ll begin to recognize some recurring patterns in how related classes are
designed, and even eventually be able to guess at some of the classes’ methods
The customized implementation benefit I just mentioned is helpful, but still for my money,
not quite enough to add so much complexity or extra work to my process. However,
before you write off interfaces, there is another much more powerful benefit to using
them that justifies the extra effort—polymorphism.