1. Abstract Class

2. Abstract Class
abstract class Shape
class Circle
extends
class Triangle
class Rectangle extends Shape Shape
extends
Shape
Java Programming: OOP 2

3. What is an Abstract Class?
• A class that is declared abstract
» Ex - abstract class Demo
» It may or may not use abstract
methods
Java Programming: OOP 3

4. What is an Abstract Method ?
• A method that is declared abstract
• A method that is declared without an
implementation
– Ex - abstract void add(int x, int y);
Java Programming: OOP 4

5. Example
public abstract class Shape {
//Abstract method i.e no implementation
abstract void Area();
}
public class Rectangle extends Shape { public class Circle extends Shape {
@Override @Override
void Area() { void Area() {
Double area = length * width; Double area = 3.14 * radius*radius;
}
} }
} Java Programming: OOP 5

6. Interface

7. Interface
• Interfaces are declared using
the interface keyword
• Interface can contain :
» method signature
(no implementation)
» constant declarations
(variable declarations that are declared to be both static and final)
Java Programming: OOP 7

8. Interface
• A class that implements an interface must implement
all of the methods described in the interface
implements
Interface Class
abstract Method1(); abstract Method1();
abstract Method2(); abstract Method2();
abstract Method3(); abstract Method3();
Java Programming: OOP 8

9. How to create an Interface
public interface Demo_interface {
int add(int value1, int value2); Demo_interface
void print(int sum);
int add(int value1, intvalue2);
void print(int sum);
}
Java Programming: OOP 9

10. How to implement the Interface
public class Class1 implements Demo_interface { Demo_interface
@Override
public int add(int value1, int value2) {
int add(int value1, intvalue2);
int sum = value1 + value2;
return sum; void print(int sum);
}
@Override
public void print(int sum) {
Class1
System.out.println("The sum is : " + sum);
}
public int add(int value1, int value2);
}
Java Programming: OOP public void print(int sum); 10

11. Using it in the main class
public class Execute {
public static void main(String[] args) {
Execute
Class1 ob = new Class1();
ob
int sum = ob.add(10, 10);
sum = ob.add(10,10);
ob.print(sum);
ob.print(sum);
}
}
Java Programming: OOP 11

12. Enums in Java

13. Enumeration
• Enumerations helps to relate Select one
the variables with related Sunday
constants so that it will be Monday
Tuesday
flexible to work. Wednesday
• To represent we use “enum” Thursday
keyword. Friday
• It can be used in dropdown Saturday
boxes.

14. Why we need to use Enum?
• Enum is type-safe i.e any constants can not be
assigned to that variables outside the enum
definition.
• Adding new constants will be easy without
disturbing already present code.
• You can also assign different constants to variables
other than default values.

15. How to declare an Enum?
• Declaring an enum is similar to class.
• Should be declared outside the class in which it has to be used or in an
interface.
variables which will be assigned constant values
• enum Colors{
Red, Green, Blue, White, Yellow
}
name of enum 0 1 2 3 4(default constants
assigned)

16. Simple program for Enum
enum Colors_enum{red , green , blue , white , yellow}
public class Main { Output:
public static void main(String args[]) {
red
Colors_enum colors[]=Colors_enum.values(); green
for(Colors_enum c:colors) blue
{ white
System.out.println(c); yellow
}
}
}

17. How to assign constants to Enum by user
enum Chocolates{ public class Main {
dairymilk(20) , public static void main(String args[]) {
kitkat(10) , Chocolates favouritechoco=Chocolate.dairymilk;
munch(5); switch(favouritechoco)
{
int cost; case dairymilk: System.out.println(“Dairy Milk”);
Choloclates(int cost) break;
{ case kitkat: System.out.println(“Kitkat”);
break;
this.cost=cost; case munch: System.out.println(“Munch”);
} break;
}
Output: Diary Milk }
}

18. •Q& A..?

19. Thanks..!