In terms of Java, when someone asks:
what is polymorphism?
Would overloading or overriding be an acceptable answer?
I think there is a bit more to it than that.
IF you had a abstract base class that defined a method with no implementation, and you defined that method in the sub class, is that still overridding?
I think overloading is not the right answer for sure.
The clearest way to express polymorphism is via an abstract base class (or interface)
public abstract class Human{
...
public abstract void goPee();
}
This class is abstract because the goPee()
method is not definable for Humans. It is only definable for the subclasses Male and Female. Also, Human is an abstract concept — You cannot create a human that is neither Male nor Female. It’s got to be one or the other.
So we defer the implementation by using the abstract class.
public class Male extends Human{
...
@Override
public void goPee(){
System.out.println("Stand Up");
}
}
and
public class Female extends Human{
...
@Override
public void goPee(){
System.out.println("Sit Down");
}
}
Now we can tell an entire room full of Humans to go pee.
public static void main(String[] args){
ArrayList<Human> group = new ArrayList<Human>();
group.add(new Male());
group.add(new Female());
// ... add more...
// tell the class to take a pee break
for (Human person : group) person.goPee();
}
Running this would yield:
Stand Up
Sit Down
...