[Java] Runtime Polymorphism

 Runtime Polymorphism

1. Polymorphism

1) compile time polymorphism

- You overload static method in java

2) runtime polymorphism

2. Runtime Polymorphism(Dynamic Method Dispatch)

- Process in which a call to an overridden method is resolved at runtime rather than compile-time

- an overridden method is called through the reference variable of a superclass

3. Upcasting

- When reference variable of Parent class refers to the object of Child class, It is known as upcasting

class Teacher{ void run(){ System.out.println("Teacher"); } } puclic class Student extends Teacher{ void run(){ System.out.println("Student"); } public static void main(String[] args){ Teacher a = new Student(); a.run(); } }

4. Runtime Polymorphism example

package statics; class Bank { int rate(){ return 0; } } class KB extends Bank{ int rate(){ return 8; } } class HN extends Bank{ int rate(){ return 9; } } public class Test{ public static void main(String[]args){ Bank a = new KB(); Bank b = new HN(); System.out.println(a.rate()); System.out.println(b.rate()); } }  

- 8,9

5. Runtime Polymorphism with data member

- Runtime polymorphism can't be achieved by data members

class Bank { int rate = 0; } class KB extends Bank{ int rate = 10; } public class Test{ public static void main(String[]args){ Bank a = new KB(); System.out.println(a.rate); } }  

- 0