Implementing polymorphism

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

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

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

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

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

 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();
}

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

 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

 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

 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

Implementing polymorphism

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Implementing polymorphism