oops in java
TRANSCRIPT
Date:06/01/2015
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OOPs concepts in Java
What is OOP?
● Object-oriented programming (OOP)style of
programming that focuses on using objects to
design and build applications.
● Think of an object as a model of the concepts,
processes, or thing in the real world that are
meaningful to your application.
What Are Objects?
● Software objects model reaL-world objects- dog, bicycle, etc.
● Real-world objects have states and behaviors-Bicycle’s states or properties: name, color, model-Bicycle’s behaviors or action : riding, changing gears
● How do Software objects implement real-world objects?-Use variables to implement states-Use methods to implement behaviors
● An object is a software bundle of variables and related methods
Definition
● Class : -is the base design of objects
● Object :- is the instance of a class
• No memory is allocated when a class is created.
• Memory is allocated only when an object is created.
OOP FEATURES
● Abstraction
● Encapsulation
● Polymorphism
● Overriding
● Inheritance
● Interfaces
Data Abstraction
● Abstraction refers to the act of
representing essential features without
including the background details or
explanations.
● Since the classes use the concept of data
abstraction , they are known as the
abstract data types.
Encapsulation
● The wrapping up of data and functions into a
single unit is known as Encapsulation.
● The data is not accessible to the outside world
and only those functions which are wrapped in
the class can access it.
● This insulation of the data from direct access
by the program is called Data hiding or
information hiding.
Polymorphism
In polymorphism refers to a programming language
ability to process objects differently depending on
their data type or class.
More specifically, it is the ability to redefine
methods for derived classes.
For example,
given a base class shape , polymorphism enables
the programmer to define different area methods
for any number of derived classes, such as circles,
rectangles and triangles. No matter what shape an
object is, applying the area method to it will return
the correct results. Polymorphism is considered to
be a requirement of any true object-oriented
programming language (OOPL).
ExamplePublic class shape
{
int calculateArea(int width,int height)
{
return width*height;
}
float calculateArea(int radius)
{
return(22/7)*radius*radius;
}
}
public class example
{
Public static void main(string args[])
{
Shape sh=new shape();
System.out.println(sh.calculateArea(10));
}
}
Method Overriding
● We have two classes and both classes have a function
with the same name and same Parameters inheritance is
necessary.
● For Example
class B
{
public void f1(int x,int y)
{
System.out.println(x+y);
}
}
class A extends B
{
public void f1(int x,int y)
{
System.out.println(x*y);
}
public static void main(String ar[])
{
A a=new A();
a.f1(5,5);
B b=new B();
b.f1(2,3);
}
}
Inheritance● In object-oriented programming, inheritance is the
concept that when a class of objects is define, any
subclass that is defined can inherit the definitions of one
or more general classes.
● This means for the programmer that an object in a
subclass need not carry its own definition of data and
methods that are generic to the class (or classes) of
which it is a part.
● This not only speeds up program development; it also
ensures an inherent validity to the defined subclass
object .
ExamplePublic class shape
{
protected int width;
protected int height;
Int calculateArea(int x,int y)
{
Return x*y;
}
Public class dimensionshape extends shape
{
Private int depth;
Int calculateVolume()
{
Return width*height*depth;
}
Interface● An interface is a collection of abstract methods (it means
all methods are only declared in an Interface). ● A class implements an interface, thereby inheriting the
abstract methods of the interface.● And that class implements interface then you need to
defined all abstract function which is present in an Interface.
● An interface is not a class. ● Writing an interface is similar to writing a class, but they
are two different concepts. ● A class describes the attributes and behaviors of an object
and interface contains behaviors that a class implements.
Exampleinterface Idemo
{
public void findSquare(int x);
}
class Demo implements Idemo
{
public void findSquare (int x)
{
System.out.println ("Square is "+(x*x));
}
public static void main (String ar[])
{
Demo dm=new Demo ();
dm.findSquare (10);
}
}
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