Sunday, 1 November 2015

Method Overriding

Method Overriding
Method overriding :  When Subclass acquires the properties of Super class  through method then it is Method Overriding
                              Method Overriding in java is most useful features of java. Through inheritance we can reuse already existed code and through method overriding we can modify that reused code according to our requirements

Method Overriding Rules:-
  1. must be IS-A relationship (inheritance).
  2. method must have same name as in the super class
  3. method must have same parameter as in the super class.
  4. The return type of the overrided method must be compatible with super class method. If super class method has primitive data type as its return type, then overrided method must have same return type in sub class also. If super class method has derived or user defined data type as its return type, then return type of sub class method must be of same type or its sub class
  5. You cannot reduce the visibility of overloaded method in subclass.

Note- You cannot override static method in method overriding.because static method is related with class and method name with object.
dynamic/late binding polymorphism: overriding
public class Bank {
     
     
       
      int getRateOfInterest()
      {
      return 4;} 
      } 
       
      class PNB extends Bank{ 
      int getRateOfInterest(){return 9;} 
      } 
       
      class KENRA extends Bank{ 
      int getRateOfInterest(){return 6;} 
      } 
      class HDFC extends Bank{ 
      int getRateOfInterest(){return 9;} 
      } 
       
      class Test{ 
      public static void main(String args[]){ 
      PNB pnb=new PNB(); 
      KENRA kenra=new KENRA(); 
      HDFC hdfc=new HDFC(); 
      System.out.println("PNB Rate of Interest: "+pnb.getRateOfInterest()); 
      System.out.println("KENRA Rate of Interest: "+kenra.getRateOfInterest()); 
      System.out.println("HDFC Rate of Interest: "+hdfc.getRateOfInterest()); 
      } 
      }
OutPut-:
 PNB Rate of Interest: 9
KENRA Rate of Interest: 6
HDFC Rate of Interest: 9

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