Polymorphism (Java)

Polymorphism (Java)

Polymorphic” literally means “of multiple shapes” and in the context of OOP, polymorphic means “having multiple behavior.

A polymorphic method results in different actions depending on the object are referenced, also known as late binding or run-time binding.

For example 

public class Employee {

       private int id;

       private String name;

         //parameterized constructor

         public Employee(int id, String name){

             this.id = id;

             this.name = name;

         }

         //default constructor

         public Employee(){

                id = 10;

                name = "not set";

         }

         public void display(){

                System.out.println("Employee id:" + id + " name:" + name);

      }

}

public class Teacher extends Employee {//here Teacher extending(inheriting) the Employee class

   private String qualification;

   //default constructor

   public Teacher () {

        //implicit call to superclass default constructor          

        qualification = "";     

   }

   //parameterized constructor

   public Teacher(int id, String name, String qual){

      super(id,name); //call to superclass(Employee) constructor must be in first line       

      qualification = qual;

   }

  

   public void display(){//same name method but here is polymorphic in nature

        super.display(); //call to superclass(Employee) display method

        System.out.println("Qualifications :" + qualification);

   }

}

public class Test {

  public static void main(String[] args) {

  //creating Employee class references

 Employee reference1 , reference2;

        reference1 = new Employee(18, "Maverick");

        reference1.display();//call to Employee display method

            

 //Employee object can hold Teacher class object because it is a child class

        reference2 = new Teacher(13,"Tom Cruise","Actor");

        reference2.display();//call to Teacher display method

 //But if you hold the Employee object to Teacher it would give you ClassCastException

Teacher teacher;

       teacher = (Teacher)new Employee(34, "Maryam");//Casting To Teacher

teacher.display();

}

}