The document explains the concept of interfaces in programming, describing them as fully abstract classes that contain only method declarations, which must be implemented by any class that implements the interface. It details the syntax for defining and implementing interfaces, the requirements for methods and variables, and touches on partial implementations and extending interfaces. Overall, it provides a brief overview of how interfaces facilitate code organization and reuse in software development.

1. Interface
- ABBHIRAMI.M

2. What is an interface?
• Fully abstract class
• It is syntactically similar to class. It contains only method declaration.
• Once it is defined, any number of classes can implement an interface.

3. • A class can implement any no of interface.
•A class which implements the interface must define all methods in
interface.
• Interface supports dynamic method resolution at run time.

4. Defining an interface
Access interface interface_name
{
return-type method-name(parameter);
return-type method-name(parameter);
type final-variable-name = 10;
}

5. Main concept
• Methods are abstract by default.
• Variables are final and static by default.
• If an interface is declared as public, then method and variables
inside the interface declaration are public.

6. Implementing Interface
Access class class_name [extends class] [implements interface1,in2,…n]
{
class body//
}

7. • Once an interface is defined, one or more class can implement it. Using the
keyword “implements”
• If a class implements more interfaces then they should be separated by
comma.
• Methods in the interface must be contained in the class. Methods used inside
the class should be defined with a keyword “public”.
• Method signature in declaration & definition must be same.

8. interface sample
{
void display(int q);
}
Class Demo implements sample
{
public void display(int x)
{
System.out.println(x);
}
void printDetail()
{
System.out.println(“class method”);
}
}

9. Class d
{
public static void main(String arg[])throws IOException
{
Demo s = new Demo();
s. display(10);
s. printDetail()
}
}

10. Class Demo implements sample
{
public void display(int x)
{
System.out.println(x);
}
}
Class Demo1 implements sample
{
public void display(int x)
{
System.out.println(“another : “ + x);
System.out.println(“===============“);
}
}

11. Class d
{
public static void main(String arg[])
{
sample s = new Demo();
Demo1 d1=new Demo1();
s. display(10); // method in demo
s=d1;
s. display(10); // method in demo1
}
}

12. Partial Implementation
• If a class doesn’t define all the methods in interface, then the class
must be declared as abstract.

13. Variable in an interface
• If we want to share constants to more classes, interface can be used.
Interface variable
Example
{
float pi=3.14;
int flag=1;
}

14. Interfaces can be extended
Interface A
{
void display();
}
Interface B extends A
{
void display2();
}

15. Conclusion
• So for now in these slides we have discussed about a small topic
named “interface”.
• Hope you get a little bit of what interface exactly is.