II – UNIT
1. Procedure Oriented Programming
2. Object Oriented Programming Paradigm
3. Basic Concepts of OOPS
4. Benefits of OOPS
5. Class fundamentals
6. Declaring Objects
7.Assigning Object References
8. Introducing Methods
9. Constructors
10. this keyword
11. Garbage Collection
12. finalize ( ) Method
13. Overloading Methods
14. Object as parameters
15. Returning Objects
16. Access Control
17. static and final keyword
18. Nested classes and Inner Class
19. Classes with Command Line
arguments
20.Packages
21.Enums in Java
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PROCEDURE ORIENTED PROGRAMMING
1. In Procedural programming, Programmer combines related sequences of
statements into one single place, called procedure.
2. A procedure call is used to invoke the procedure.
3. After the sequence is processed, flow of control proceeds right after the
position where the call was made.
4. But the approach in oops is that classes and objects are used to model real
world entity taking help of methods which performs the functions.
5. This technique is also known as Top – down programming
OBJECT ORIENTED PROGRAMMING PARADIGM
1. The major objective of object oriented approach is to eliminate some of the
flaws encountered in the procedural approach.
2. OOP treats data as a critical element to the program development and does
not allow it to flow freely around the system.
3. It ties data more closely to the function that operate on it an protects it2from
unintentional modification by other functions.
4. OOP allows us to decompose a problem into a number of entities called
Objects and then build data and functions (known as methods in Java)
around these entities.
5. The combination of data and methods make up an object
Methods
Methods
Data
Methods
Methods
Object = Data + Methods
6. The data of an object can be accessed only by the methods associated with
that object.
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7. However, methods of one object can access the methods of other object.
Procedural vs. Object-Oriented
Procedural
Withdraw, deposit, transfer
Object-Oriented
Customer, money, account
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Procedural vs. Object-Oriented – Contd.,
• Real world Objects are mapped to software in OOPs
• Objects in the problem domain are mapped to objects in
software
Questions
• What are Objects?
• What are Classes?
• What are Messages?
Answers
• Objects reflect instances that embody those concepts.
• Classes reflect concepts.
• Messages are communication between objects.
object
Rita
class
Gita
Sita
Mita
What are Objects?
• “An object is a software bundle of variables and related methods”
• Software objects are model real-world objects or abstract concepts
• Real-world objects have states and behaviors
– Dogs' states: name, color, breed, hungry
– Dogs' behaviors: barking fetching
• Software objects implement real-world objects by:
– Using variables to implement states
– Using methods to implement behaviors
Visual Representation of a Software Object
8. Some of the features of object oriented paradigm are:
•
Emphasis is on data rather than procedure.
•
Programs are divided into what are known as Objects.
•
Data Structures are designed such that they characterize the objects.
•
Methods that operate on the data of an object are tied together in the
data structure.
•
Data is hidden and cannot be accessed by external functions.
•
Objects may communicate with each other through methods.
•
New data and methods can be easily added whenever necessary.
•
Follows bottom – up approach in program design.
9. Our definition of object oriented programming is: Object oriented
programming is an approach that provides a way of modularizing
programs
by creating partitioned memory area for both data and function that
can be
used as templates for creating copies of such modules on demand.
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BASIC CONCEPTS OF OBJECT ORIENTED PROGRAMMING
1. Class
2. Objects
3. Data Abstraction
4. Data Encapsulation
5. Data Hiding
6. Inheritance
7. Polymorphism
8. Dynamic Binding
9. Message Communication
1. Class
The entire set of data and code of an object can be made a user – defined data
type using the concept of a class. A class may be thought of as a ‘data type’ and an
object as a ‘variable’ of that data type. Once a class has been defined, we can create
any number of objects belonging to that class. Each object is associated with the
data of type class with which they are created. A class is thus a collection of objects
of similar type.
2. Objects
Objects are the basic runtime entities in an object – oriented system. They may
represent a person, a place, a bank account, a table of data or any item that the
program may handle. They may also represent user – defined data types such as
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vectors and lists. Any programming problem is analyzed in terms of objects and
the
nature of communication between them.
What are Classes?
• A class is a blueprint or prototype defining the variables
and methods common to all objects of a certain kind.
• An object is an instance of a certain class.
• After you have created a class, you must create an
instance of it before you can use.
• The benefit of Classes: Reusability
• A class captures the common properties of the objects
instantiated from it
• A class characterizes the common behavior of all the
objects that are its instances
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CLASS Example
class Account
{
private String accountName;
private double accountBalance;
public withdraw();
public deposit();
public determineBalance()
}
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OBJECTS
• Object-oriented is a way of looking at a Software System as a collection of
interactive objects
• Object is an instance of a class
• Object represents an entity either physically, conceptual, or software.
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OBJECTS
• All the objects share the same attribute names and methods with other
objects of the same class.
• Each object has its own value for each of the attribute.
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CLASSES / OBJECTS
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OBJECTS
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What goes inside a class
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ADDING METHODS
• A Class with only data fields has no life. Objects created by such a class cannot
respond to any messages.
• Methods are declared inside the body of the class but immediately after the
declaration of data fields.
The general form of a method declaration is:
type methodName (Paramter-list)
{
method-body;
}
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ADDING METHODS TO CLASS CIRCLE
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CREATING OBJECTS OF A CLASS
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CREATING OBJECTS OF A CLASS
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Accessing Object Data
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EXECUTING METHODS ON OBJECT
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BASIC PRINCIPLES OF OO
Encapsulation
Data Abstraction
OOP
Paradigm
Inheritance
Polymorphism
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Encapsulation
• It associates the code and the
data it manipulates into a single
unit; and keeps them safe from
external
interference
and
Encapsulation
misuse
OOP
Paradig
m
Data
Abstraction
Inheritance
Polymorphism
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ENCAPSULATION
• All information (attributes and methods) in an object oriented system
are stored within the object/class.
• Information can be manipulated through operations performed on
the object/class – interface to the class. Implementation is hidden
from the user.
• Object support Information Hiding – Some attributes and methods
can be hidden from the user
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ENCAPSULATION - Example
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Without Encapsulation?
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With Encapsulation
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INHERITANCE
• New data types (classes) can be defined as
extensions to previously defined type.
• Parent Class ( Super Class ) –Child Class (
Encapsulation
Sub Class)
• Subclass inherits properties from the class
OOP
Paradig
m
Data
Abstraction
Inheritance
Polymorphism
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INHERITANCE - Example
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INHERITANCE - Example
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INHERITANCE - Example
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Polymorphism
Encapsulatio
n
OOP
Paradi
gm
Data
Abstraction
Inheritance
• An Object of type circle or
rectangle can be assigned to a
Shape object. The behavior of the
object will depend on the object
passed.
Polymorphis
m
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POLYMORPHISM – Method Overloading
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ENCAPSULATION
Encapsulation
OOP
Paradigm
Data
Abstraction
Inheritance
Polymorphism
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Inheritance mechanism is that it allows the programmer to reuse a class that is almost,
but not exactly, what he wants, and to tailor the class in such a way that it does not
introduce any undesirable side effects into the rest of the classes. In java, the derived
class is known as ‘subclass’
Bird
Attributes:
Feathers
Lay eggs
Flying Bird
Non FlyingBird
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7. Polymorphism
Polymorphism is another important OOP concept. Polymorphism means the
ability to take more than one form. For example, an operation may exhibit different
behaviour in different instances. The behaviour depends upon the types of data used in
the operation. For example consider the operation of addition. For two number, the
operation will generate a sum. If the operands are strings, then the operation would
produce a third string by concatenation. Consider the following example:
Shape
Draw()
Circle Object
Box Object
Triangle Object
Draw(circle)
Draw(box)
Draw(triangle)
Polymorphism plays an important role in allowing objects having different
interval structures to share the same external interface. This means that a general class
of operations may be accessed in the same manner even though specific actions
associated with each operation may differ. Polymorphism is extensively used
in
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implementing inheritance.
Network of objects communicating between them
Object 1
Object 5
Object 2
Object 3
Object 4
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Benefits of OOPS
1. Through inheritance, we can eliminate redundant code and extend the use of
existing classes.
2. We can build programs from the standard working modules that
communicate with one another, rather than having to start writing the code
from scratch. This leads to saving of development time and higher
productivity.
3. The principle of data binding helps the programmer to build secure programs
that cannot be invaded by code in other parts of the program.
4. It is possible to map objects in the problem domain to those objects in the
program.
5. It is possible to have multiple objects to coexist without any interference.
6. It is easy to partition the work in a project based on objects.
7. The data – centered design approach enables us to capture more details of
a model in an implementable form.
8. Object – Oriented systems can be easily upgraded from small to large
systems.
9. Message passing techniques for communication between objects make the
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interface descriptions with external systems much simpler.
Application of OOPS
1. Real – time systems.
2. Simulation and modelling.
3. Object – oriented databases.
4. Hypertext, hypermedia and expertext.
5. AI and expert systems.
6. Neural networks and parallel programming.
7. Decision support.
8. Office automation systems.
9. CIM / CAD / CAM system.
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The Java Buzzwords or Java Features or Java Characteristics
■ Simple
■ Secure
■ Portable
■ Object-oriented
■ Robust
■ Multithreaded
■ Architecture-neutral
■ Interpreted
■ High performance
■ Distributed
■ Dynamic
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Methods Introductions
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Introduction
• Methods are nothing but function.
• It is a set of statements which can be included in java
class.
• It can be called at any point in java class by simply
calling method name.
• Methods have so much of power and flexibility.
• Methods should be declared in the class.
• It can be public, private, and protected.
• Methods are of two types, one is with argument and
another is without argument.
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Types of Methods
• Methods are used to access the data fields in a class
• These methods are linked with the objects
• Class creates an object using new keyword, and this
object can be used for calling the methods.
• An instance method is called by prefixing it with an
object
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• Methods can be declared using various types such as
1. Return type method -returns value or does not return any
values (void).
2. Modifiers – it is public private, and protected
3. Parameter – it should be listed in parentheses,().
4. Method body – declare between braces
• Method declaration
• static - class method, no need to create class
reference
• final - method cannot be overridden
• abstract - method is not implemented in another cl
• ass/method
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Empty Method
class emptymethod {
int i,j,k;
void method1() {
i=10;
j=10;
k=i*j;
System.out.println(" Result k is:"+k);}
public static void main(String args[])
{
emptymethod e=new emptymethod();
e.method1();
}}
• Output :
• Result K is 100
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Method using argument
class argument {
int i;
String st;
void meth(int a, String s) {
int i=a;
String st=s;
System.out.println("Employee Id:"+i);
System.out.println("Employee Id:"+st); }
public static void main(String args[])
{
argument obj=new argument();
obj.meth(5001,"Kumar"); }}
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Methods using return keyword
class example {
int c;
int add(int a, int b) {
return a+b; }
int subtract(int a, int b){
return a-b;}
int multiply(int a, int b){
return a*b;}
int division(int a, int b) {
return a/b; }}
class returnexa {
public static void main(String[]
args) {
example obj= new example();
obj.add(10,20);
System.out.println("Addition: "
+obj.add(30,15));
System.out.println("Subtraction: "
+obj.subtract(30,15));
System.out.println("Multiplication:
" +obj.multiply(30,15));
System.out.println("Division: " +
obj.division(30,15)); }}
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CLASS
• A Class represents a template for several objects that have common
properties
• A class defines all the properties common to the object – attributes
and methods.
• A Class is a set of attributes and operations that are performed on the
attributes.
• A Class is the blueprint from which individual objects are created.
• An object is an instance of a class
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