Java Polymorphism.

Java Polymorphism

• Polymorphism is the third essential feature of an object-oriented programming language, after data abstraction and inheritance.
• Poly means many, and morph means form: A polymorphic function is many-formed.

• Building polymorphism is :
  • The capability to bind specific derived class objects to base class reference at runtime.
  • Create Overriding methods to change the behavior of objects in the sub-classes (it is called subtype polymorphism).
  A polymorphism example:

  class Vehicle {
  
    static int wheels = 4;
  
    public String Status() {
      return "I am a Vehicle with " + wheels + " wheels";
    }
  }
  
  class Trailer extends Vehicle {
  
    static int wheels = 16; // this hides statics wheels in Vehicle
  
    @Override   
    public String Status() {
      return "I am a Trailer with " + wheels + "  wheels";
    }
  }
  
  public class PolymorphismDemo {
  
    public static void main(String args[]) {
      Vehicle a = new Vehicle();      // Vehicle reference to an Vehicle object
      Vehicle b = new Trailer();      // Vehicle reference to a Trailer object
      System.out.println(a.Status()); // Runs the method in Vehicle class
      System.out.println(b.Status()); // Runs the method in Trailer class
    }
  }

  The result of this is:

  I am a Vehicle with 4 wheels
  I am a Trailer with 16  wheels

  You can download this example here (needed tools can be found in the right menu on this page).