Inheritance,single,multiple.access rulepptx

java

1. I nheritance I n J ava presented by: Hannah Roseline .R Sri Ramakrishna college of arts &science.

2. I nheritance : In java inheritance is a mechanism which one object can get all the properties and behaviours of a parent object. In inheritance there is a relationship between two classes. That’s why it is-a relationship . For example : Bike, car, bus this are vehicle. That’s why the child of vehicle are bike, car, bus and vehicle is the parent of this objects. Vehicle Bike, car, bus

3. J ava inheritance : The important of inheritance in java program is code reusability . We can reuse the function of parent class at child class. In java we use Extends keyword for inheritance. Subclass and Superclass in inheritance.

4. I nheritance Syntax : class Parent { //code } class Child extends Parent { //code } Parent Child

5. S imple program class super { Public void display() { System.out.println (“I am parent class”); } } class sub extends super { public static void main(String args []) { sub message = new sub() message.display (); } } Super I am from parent class sub Parent class Child classs Output: I am parent class

6. T ypes of inheritance: Single inheritance. Multiple inheritance. Multi-level inheritance. Hierarchical inheritance. Hybrid inheritance. Note: In java Multiple inheritance is not supported.

7. S ingle inheritance: Single inheritance is the most easy type to understand. In single inheritance a class extends another only one class. The child class inherit only parents class. The subclass inherit the objects of superclass. Example: A cat is a animal. So a cat only can inherit the objects of animal class. Animal (superclass) Cat (subclass)

8. S ample program of single inheritance : class message_super { Public void display() { System.out.println (“I am from superclass”); } } class message_sub extends message_super { public static void main(String args []) { Message_sub message = new message_sub () Message.display (); } } Output: I am from superclass message_super I am from superclass message_sub

9. M ultilevel inheritance When a class extends a class, and that class extends another class and its object then it call multilevel inheritance. Example: a class A is parent class. Class B is inherit the objects of class A. Another one class c is child of class B. class c can inherit the objects of class C. A B C Base class Intermediary class Child class

10. S ample program of multilevel inheritance : class a { int data= 15; } class b extends a { } class c extends b { public void display() { System.out.println (“number is:”+data); } public static void main(String args []) { c num = new c() num.display (); } } Output: number is: 15 a Data=15 b c

11. H ierarchical inheritance: When one superclass can be inherited by more than one subclass then it is called hierarchical inheritance. Example: a class A is parent class. Class B is inherit the objects of class A. Another one class c also can inherit the objects of class A. A B C

12. Syntax of Hierarchical inheritance: Class Food { //code } class Rice extends Food{ //code } class Fruit extends Food{ //code } Food Rice Fruit

13. Inheritance Method overriding: When a method is already in parent class but also declaring in child class, then it is known as Method Overriding. Note: But when it is ‘Final’ method it cannot overriding. Example: A parent class of animal has method ‘eat’. Also a child class tiger has method ‘eat’. Animal eat() Tiger eat()

14. Sample program of method overriding: class animal { public void display() { System.out.println (“I am animal”); } } class tiger extends animal { public void display() { System.out.println (“I am tiger”); } public static void main(String args []) { tiger t = new tiger(); t.display (); } } Output: I am tiger

15. Introduction: Polymorphism poly=many morphism=forms i.e one interface having many methods. Polymorphism simply means many forms. It can be defined as one thing performing different forms .

16. Method Overriding in Java If subclass (child class) has the same method as declared in the parent class, it is known as  method overriding in java . In other words, If subclass provides the specific implementation of the method that has been provided by one of its parent class, it is known as method overriding. Usage of Java Method Overriding Method overriding is used to provide specific implementation of a method that is already provided by its super class. Method overriding is used for runtime polymorphism Rules for Java Method Overriding method must have same name as in the parent class method must have same parameter as in the parent class.

17. Super keyword in java Super keyword is a reference variable that is used for refer parent class object. Super Keyword is mainly used at three level in java At variable level At method level At constructor level

18. Why use super keyword in java? Whenever inherit base class data into derived class it is chance to get ambiguity ( தெளிவின்மை ) , because may be base class and derived class data are same so to difference these data need to use super keyword

19. Example of Super Keyword class Employee { float salary=10000; } class HR extends Employee { float salary=20000; void display() { System. out .println ("Salary: "+ super .salary );//print base class salary } } class Supervarible { public static void main(String[] args ) { HR obj= new HR(); obj.display (); } }

20. Thank you