What is polymorphism, what is it for, and how is it used?

Question

What is polymorphism, what is it for, and how is it used?

Answer 1

In Object Oriented languages, polymorphism allows treatment and handling of different data types through the same interface. For example, consider inheritance in C++: Class B is derived from Class A. A pointer of type A* (pointer to class A) may be used to handle both an object of class A AND an object of class B.

Answer 2

Polymorphism in coding terms is when your object can exist as multiple types through inheritance etc. If you create a class named "Shape" which defines the number of sides your object has then you can then create a new class which inherits it such as "Square". When you subsequently make an instance of "Square" you can then cast it back and forward from "Shape" to "Square" as required.

Answer 3

Let's use an analogy. For a given musical script every musician which plays it gives her own touch in the interpretation.

Musician can be abstracted with interfaces, genre to which musician belongs can be an abstrac class which defines some global rules of interpretation and every musician who plays can be modeled with a concrete class.

If you are a listener of the musical work, you have a reference to the script e.g. Bach's 'Fuga and Tocata' and every musician who performs it does it polymorphicaly in her own way.

This is just an example of a possible design (in Java):

public interface Musician {
  public void play(Work work);
}

public interface Work {
  public String getScript();
}

public class FugaAndToccata implements Work {
  public String getScript() {
    return Bach.getFugaAndToccataScript();
  }
}

public class AnnHalloway implements Musician {
  public void play(Work work) {
    // plays in her own style, strict, disciplined
    String script = work.getScript()
  }
}

public class VictorBorga implements Musician {
  public void play(Work work) {
    // goofing while playing with superb style
    String script = work.getScript()
  }
}

public class Listener {
  public void main(String[] args) {
    Musician musician;
    if (args!=null && args.length > 0 && args[0].equals("C")) {
      musician = new AnnHalloway();
    } else {
      musician = new TerryGilliam();
    }
    musician.play(new FugaAndToccata());
}

Answer 4

In object-oriented programming, polymorphism refers to a programming language's ability to process objects differently depending on their data type or class. More specifically, it is the ability to redefine methods for derived classes.