Question

I am novice in programming, I want to ask that what is the ultimate use of run-time polymorphism?

Example:

class Parent
{
    //do something
}
class Child : Parent
{
    //do something
}

main()
{
    Parent p = new Child (); // run-time polymorphism
    Child q = new Child(); // no polymorphism
}

My question is that, we use first line (Parent p = new Child();) to achieve runtime polymorphism, but we can use second line (Child q = new Child();) in lieu of first one….

So what is the difference between both of them? Why do we use run-time polymorphism?

Answer 1

There’s no actual use for the code snippet you’ve provided. But think about this method:

public void DoSomething( Parent parent ){ ... }

You can do this:

Child child = new Child();
DoSomething( child );

In this case, for DoSomething it will be just a Parent. It doesn’t care if it is a subclass or not.

Hope it helps.