inheritance and interface in oops with java .pptx

Contents
🠶 Introduction to inheritance
🠶 Types of Inheritance
🠶 Method overriding using
inheritance
🠶 Super keyword
🠶 Final keyword
🠶 Interfaces

Introduction to inheritance
🠶 As the name suggests, inheritance means to take something that is already
made.
🠶 Inheritance is a unique feature of object oriented programming.
🠶 Inheritance is mainly used for code reusability.
🠶 The class which acquires the properties of the class is called as sub-class and
the class whose properties are acquired is called as superclass.
Consider the example:
As shown in example, the child inherit the properties
of father. Hence child will be subclass while father is a
superclass.

IS-A Relationship
🠶 Inheritance defines IS-A relationship between a super class and its subclass
🠶 For Example:
🠶 Car IS A vehicle
🠶 Bike IS A vehicle
🠶 EngineeringCollege IS A college
🠶 MedicalCollege IS A college
🠶 In java, inheritance is implemented with the help of keyword - “extends”.

Types of
inheritance
• Single inheritance
• Multilevel inheritance
• Hierarchical
inheritance

Single Inheritance
🠶 A structure having one and only one super class as well as
subclass.
🠶 Child class is authorized to access the property of Parent class.
Super
class
Subclass
Syntax
:
class A
{
………….
………….
}
class B extends
A
{
………….
………….
}
Sharing of
properties

Multilevel inheritance
B
C
A
🠶 When a class is derived from a class
which is also derived from a class,
then such type of inheritance is called
as multilevel inheritance.
Syntax
:
class A
{
………….
………….
}
class B extends
A
{
………….
………….
}
class C extends
B
{
………….
………….
}

Hierarchical inheritance
🠶 In hierarchical inheritance, one class
is inherited by many subclasses.
🠶 subclasses must be connected with
only
one super class.
B D
A
C
Syntax :
class A
{
…
……
….
…
……
….
}
class B
extends
A
{
…
……
….
…
……
….
}

Why multiple inheritance is not supported in java ?
🠶 To reduce the complexity and simply the language, java doesn’t
support
multiple inheritance.
🠶 Suppose there are 3 classes A,B and C. The C class inherits class A and
B.
🠶 If A and B have same method and you call it from child class object,
there will be ambiguity to call method of A or B class.
🠶 Since compile time errors are better than run time errors, java renders
compile time error if you inherit 2 classes.

Access Specifiers in java
🠶 There are four Access Specifiers in Java
🠶 1. Public: When a member of a class is declared as public specifier, it can
be accessed from any code.
🠶 2. Protected: Protected is only applicable in case of Inheritance. When a
member of a class is declared as protected, it can only be accessed by
the members of its class or subclass.
🠶 3. Private: A member of a class is declared as private specifier, can only
be accessed by the member of its class.
🠶 4. Default: When you don't specify a access specifier to a member, Java
automatically specifies a default. And the members modified by default can
only be accessed by any other code in the package, but can't be accessed
outside of a package.

A program demonstrating inheritance in Java
1. class circle{
2. double radius;
3. void radius(double a)
4. {
5. radius=a;
6. }
7. double getdata()
8. {
9. double area;
10.area=3.14*radius*radius;
11.return area;
12.}
13.}
14.class cylinder extends circle{
15.double h;
16.void height(double b,double
r)
17.{
18.radius=r;
19.h=b;
20.}
21.double getdata()
22.{
23.double volume;
24.volume=3.14*radius*radius*h;
25.return volume;
26.}

A program demonstrating inheritance in Java
27.public static void main(String[] args) {
28.cylinder c1=new cylinder();
29.c1.height(5.12,6.5);
30.double area,volume;
31.volume=c1.getdata();
32.System.out.println("Volume of
cylinder :"+volume);
33.circle ob=new circle();
34.ob.radius(4.44);
35.ob.getdata();
36.area=ob.getdata();
37.System.out.println("area of circle:"+area);
38.}
39.}
Output of program:
Volume of cylinder :679.2447999999
Area of circle:61.90070400000001

Method overriding in Java
Subclasses inherit all methods from their superclass
Sometimes, the implementation of the method in the superclass does
not
provide the functionality required by the subclass.
In these cases, the method must be overridden.
To override a method, provide an implementation in the subclass.
The method in the subclass MUST have the exact same signature as the
method it is overriding.

Program demonstrating method
overriding
1. class A{
2. void display()
3. {
4. System.out.println("This is parent
class.");
5. }
6. }
7. class B extends A{
8. void display()
9. {
10.System.out.println("This is first child
class");
11.}
12.public static void main(String[] args)
{
13.B b1=new B();
14.b1.display();
15.}
16.}
Output:
This is first child class

Super keyword
🠶 As the name suggest super is used to access the members of the super class.
🠶 It is used for two purposes in java.
1. The first use of keyword super is to access the data variables of the super class
hidden by the sub class.
🠶 e.g. Suppose class A is the super class that has two instance variables as int a
and float b.
🠶 class B is the subclass that also contains its own data members named a and
b.
🠶 Then we can access the super class (class A) variables a and b inside the
subclass class B just by calling the following command.
🠶 super.member;

Super keyword
🠶 2.Use of super to call super class constructor: The second use of the
keyword super in java is to call super class constructor in the subclass.
🠶 This functionality can be achieved just by using the following command.
super(param-list);
🠶 Here parameter list is the list of the parameter requires by the
constructor in the super class.
🠶 super must be the first statement executed inside a super class constructor.
🠶 If we want to call the default constructor then we pass the
empty parameter list.
🠶 If we dont use super then the compiler does this task implicitly to
instantiate
superclass members.

Program to demonstrate Super Keyword
1) class Animal{
2) Animal(){System.out.println("animal is created");}
3) }
4) class Dog extends Animal{
5) Dog(){
6) super();
7) System.out.println("dog is created");
8) }
9) }
10) class TestSuper3{
11) public static void main(String args[]){
12)Dog d=new
Dog(); 13)}}
Output:
Animal is created
Dog is created

Final Keyword
🠶 The final keyword in java is used to restrict the user.
🠶 The final keyword can be used in mainly 3 context.
1. Variable: If you make any variable final, you cannot change the
value of final variable.
Example:
1. class bike{
2. final int speedlimit=50;
3. void run(){
4. speedlimit=60; //Compile-
time error
5. }
6. public static void main(String[] args){
7. Bike ob=new bike();
8. ob.run();
9. }
10. }
Output:
Compile time
error

Final keyword
2. Method: If you make a method final, you cannot override
it.
Example:
1. class bike{
2. final void run(){
3. System.out.println(“Running”);
4. }
5. class honda extends run(){
6. void run(){ //compile time error
7. System.out.println(“Running at 100 kmph”);
8. }
9. }
10. public static void main(String[] args)
{
11. Bike ob=new bike();
12. ob.run();
13. }
14. }
Output:
Compile time
error

Final keyword
3. Class : If you make any class final, you cannot extend it.
Example:
1. final class bike{
2. //code here
3. }
4. class honda extends run(){ //Compile
time error
5. void run(){
6. System.out.println(“Running at 100 kmph”);
7. }
8. public static void main(String[] args){
9. honda ob=new honda();
10. ob.run();
11. }
12. }
Output:
Compile time
error

Interface in Java
🠶 Java Supports a special feature called
interface.
🠶 This feature helps to connect a class with more than
one classes (in order to achieve multiple
inheritance).
🠶 For this type of connectivity java uses
‘implements’
keyword.
🠶 A class can implements multiple interfaces at a
same time
🠶 All the variables defined in the interface are final
and
cannot be changed in subclass.
Syntax :
interface A
{
int a=10;
public int getdata();
public void display();
}
interface B
{
public void
getmarks();
}
class D implements A,B
{
………..
………..

Comparison between interface and abstract class
Features Interface Abstract class
Multiple inheritance A class may
implement multiple
interfaces
A class can extend only
one abstract class
Default implementation An interface cannot provide
any code at all
An abstract class can
provide complete code,
default code
Constants Constants are by
default Static and final
Both static and
instance constants are
allowed
Object An object of interface
is never created
An object of abstract
class can be created

Program demonstrating interfaces
1. interface Printable{
2. void print();
3. }
4. interface Showable{
5. void show();
6. }
7. class A7 implements Printable,Showable{
8. public void print(){System.out.println("Hello");}
9. public void show(){System.out.println("Welcome");}
10. public static void main(String args[]){
11.A7 obj = new
A7();
12.obj.print();
13.obj.show();
14. }
15. }
Output:
Hello
Welcome

inheritance and interface in oops with java .pptx

More Related Content

Similar to inheritance and interface in oops with java .pptx (20)

More from janetvidyaanancys (16)

Recently uploaded (20)

inheritance and interface in oops with java .pptx