The document discusses polymorphism and interfaces in object-oriented programming. It defines polymorphism as an object being able to take on multiple forms and provides the example of a parent class reference referring to a child class object. Interfaces are described as allowing polymorphism to be defined declaratively separate from implementation. The key points are that interfaces define methods but do not implement them, classes implementing interfaces must implement the interface methods, and interfaces can extend other interfaces similar to class inheritance.

1. M.Rajshree
II-MSC(IT)
Nadar saraswathi college of arts&science

2. Polymorphism is the ability of a message to
be displayed in more than one form
 The most common use of polymorphism in
OOP occurs when a parent class reference is
used to refer to a child class object.
Any Java object that can pass more than one a
test is considered to be polymorphic

3. Create a completely separate class specific to
each type of object
These object classes would share a lot of
members in common, but they would be
completely separate from each other
for example, that had the generic object
members such as the speed property and the
travel method

4. There is another object oriented
Programming concept that is closely related
to abstract classes called interface
Interfaces allow us to define polymorphism
in a declarative way unrelated to
implementation
In interfaces, you can only define (not
implement) methods inside the parent class

5. Use the concept of an Interface class that will
define (but will not implement) common
properties and methods for the more specific
classes
Create separate classes then implement each
specific type of object that you will need
And that use the interface class to specify
common functionality

6.  The classes that implement the Interface must
implement all members of the Interface
 An Interface is a class that has only a method
body but no implementation
Example:
public interface shape
{
void draw();
}

7. Shape is an interface with only one method,
i.e. draw(). Basically, it is a contract that when
you are implementing that interface, you have
to implement the draw functionality, or else
you are not a complete class
 So for any class like Triangle or Rectangle,
when we implement that Interface, they must
implement the draw() method

8.  We sometimes use an arraylist, we are not as
concerned about how the feature set by the list
interface have been implemented by arraylist
Example :
List l = New ArrayList();
l.add()
 we needed to use an LinkedList instead of
an ArrayList, we could easily do that by changing:
List l = new LinkedList();
 ArrayList used in our program because we used
them through the contract published by the Interface

9.  The methods cannot be implemented inside the
interface
 Variables (properties) cannot be defined inside the
interface
 All the methods defined inside the interface need to
be implemented in the child class
 All the necessary variables need to be defined
inside the child class
 Man interface enforces its implementing classes to
implement all the methods in the interface

10.  Implementation interfaces, there are several
rules a class can implement more than
one interface at a time
A class can extend only one class but it
implement many interfaces
An interface can extend another interface in
a similar way as a class can extend another
class

11. Thank you