The document discusses object-oriented programming concepts in Java such as inheritance, polymorphism, abstraction, and encapsulation. It defines inheritance as extending existing classes and reusing their properties to create new classes. There are different types of inheritance like single, multilevel, hierarchical, and multiple inheritance using interfaces. The document also discusses access modifiers, abstract classes and methods, interfaces, packages, and other OOP concepts in Java.

1. Derived conceptsDerived concepts
By
Nilesh Dalvi
Lecturer, Patkar-Varde College.Lecturer, Patkar-Varde College.
http://www.slideshare.net/nileshdalvi01
Java and Data StructuresJava and Data Structures

2. Inheritance
• Inheritance is one of the most useful and essential
characteristics of oops.
• Existing classes are main components of
inheritance.
• New classes are created from existing one.
• Properties of existing classes are simply extended
to the new classes.
• New classes are called as derived classes and
existing one are base classes.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

3. Types of Inheritance
1. Single Inheritance
2. Hierarchical Inheritance
3. Multilevel Inheritance
4. Hybrid Inheritance
5. Multiple Inheritance (Interfaces)
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

4. Types of Inheritance
Single inheritance:
A derived class with only one base class is
called as single inheritance.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

5. Types of Inheritance
Multilevel inheritance:
The mechanism of deriving a class from
another ‘derived class’ is known as multilevel
inheritance.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

6. Types of Inheritance
Hierarchical inheritance:
One class may be inherited by more than one
class. This process is known as hierarchical
inheritance.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

7. Types of Inheritance
Hybrid inheritance:
It is combination of Hierarchical and Multilevel
inheritance.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

8. Types of Inheritance
Multiple inheritance (Interfaces):
A derived class with several base classes is
called as Multiple inheritance.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

9. Defining Sub class
• A Sub class can be defined by specifying its relationship with
the super class in addition to its own details.
class sub-class-name extends super-class-name
{
//members of sub class.
}
• The extends indicates that the properties of super class are
extended to the sub class.
• Sub class contain its own properties as well as those of the
super class.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

10. Visibility Control
• It is also known as access modifiers.
• Java provides:
– Public access
– Friendly access (Default)
– Protected access
– Private access
– Private protected access
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

11. Visibility Control
Public access:
• Any variable or method is visible to the entire
class in which it is defined.
• But, to make a member accessible outside
with objects, we simply declare the variable or
method as public.
• A variable or method declared as public has
the widest possible visibility and accessible
everywhere.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

12. Visibility Control
Friendly access:
• When no access modifier is specified, the member
defaults to a limited version of public accessibility
known as "friendly" level of access.
• The difference between the "public" access and the
"friendly" access is that the public modifier makes
fields visible in all classes, regardless of their
packages while the friendly access makes fields
visible only in the same package, but not in other
packages.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

13. Visibility Control
Protected access:
• The visibility level of a "protected" field lies in
between the public access and friendly access.
• That is, the protected modifier makes the fields
visible not only to all classes and subclasses in the
same package but also to subclasses in other
packages
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

14. Visibility Control
Private access:
• Private fields have the highest degree of protection.
• They are accessible only with their own class.
• They cannot be inherited by subclasses and
therefore not accessible in subclasses.
• Method declared as private behaves like final
method .
• It prevents the method from being sub classed.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

15. Visibility Control
Private protected access:
• A field can be declared with two
keywords private and protected together.
Eg. private protected int codeNumber;
• This gives a visibility level in between the "protected"
access and "private" access.
• This modifier makes the fields visible in all subclasses
regardless of what package they are in.
• Remember, these fields are not accessible by other
classes in the same package.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

16. Visibility Control
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

17. Single inheritance
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class Room
{
int length;
int breadth;
Room (int x, int y)
{
length = x;
breadth = y;
}
int area ()
{
return(length * breadth);
}
}

18. Single inheritance
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class BedRoom extends Room
{
int heigth;
BedRoom(int x, int y, int z)
{
super (x, y);
height = z;
}
int volume ()
{
return (length * breadth * height);
}
}

19. Single inheritance
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class IntDemo
{
public static void main(String args [])
{
BedRoom b = new BedRoom(14, 12, 10);
System.out.println("Area :" + b.area());
System.out.println("Volume :" + b.volume());
}
}

20. super keyword
• The super is a reference variable that is used
to refer immediate parent class object.
• Usage of super Keyword
– super is used to refer immediate parent class
instance variable.
– super() is used to invoke immediate parent class
constructor.
– super is used to invoke immediate parent class
method.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

21. super keyword
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
//refer immediate parent class instance variable.
class Vehicle
{
int speed = 50;
}
class Bike extends Vehicle
{
int speed = 100;
void display()
{
System.out.println(super.speed);
}
public static void main(String args[])
{
Bike b=new Bike();
b.display();
}
}

22. super keyword
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
//invoke parent class constructor.
class Vehicle
{
Vehicle()
{
System.out.println("Vehicle is created");
}
}
class Bike extends Vehicle
{
Bike()
{
super();//will invoke parent class constructor
System.out.println("Bike is created");
}
public static void main(String args[])
{
Bike b=new Bike();
}
}

23. super keyword
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
// super can be used to invoke parent class method.
class Person
{
void message(){
System.out.println("welcome");
}
}
class Student extends Person
{
void message(){
System.out.println("welcome to java");
}
void display(){
message();
super.message();
}
public static void main(String args[]){
Student s=new Student();
s.display();
}
}

24. Method Overriding
• If subclass (child class) has the same method as declared in
the parent class, it is known as method overriding.
• Advantage of Java Method Overriding
– Method Overriding is used to provide specific implementation of a
method that is already provided by its super class.
– Method Overriding is used for Runtime Polymorphism
• Rules for Method Overriding
– method must have same name as in the parent class
– method must have same parameter as in the parent class.
– must be IS-A relationship (inheritance).
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

25. Method Overriding
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class Vehicle
{
void run()
{
System.out.println("Vehicle is running");
}
}
class Bike extends Vehicle
{
void run()
{
System.out.println("Bike is running safely");
}
public static void main(String args[])
{
Bike obj = new Bike();
obj.run();
}
}

26. final keyword
• It is used to restrict the user.
• The final keyword can be used in many context.
• Final can be:
– Variable
– Method
– class
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

27. final Variable
• If you make any variable as final, you cannot change
the value of final variable(It will be constant).
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class Bike
{
final int speedlimit=90;
void run()
{
speedlimit=400;
}
public static void main(String args[])
{
Bike obj=new Bike();
obj.run();
}
}

28. final Method
• If you make any method as final, you cannot override
it.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class Bike
{
final void run() {
System.out.println("running");
}
}
class Honda extends Bike
{
void run() {
System.out.println("running safely
with 100kmph");
}
public static void main(String args[]){
Honda honda= new Honda();
honda.run();
}
}

29. final Class
• If you make any class as final, you cannot extend it.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
final class Bike{}
class Honda extends Bike
{
void run()
{
System.out.println("running safely
with 100kmph");
}
public static void main(String args[])
{
Honda honda= new Honda();
honda.run();
}
}

30. Abstract Modifier
• It is applied to
– Class
– Method
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

31. Abstract Class
• An abstract class never be instantiated.
• If a class is declared as abstract then, the sole purpose is for
the class to be extended.
• A class can not both final and abstract.
• If class contain abstract method, the class should be declared
abstract otherwise compile time error thrown.
• Abstract class may contain both abstract and normal
methods.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
abstract class shape
{
-----------
-----------
abstract void draw();
-----------
}

32. Abstract Method
• It is a method declared without any implementation .
• Method body provided by sub class
• Never be final
• Any class that extends abstract class must implement all the
abstract method of super class, unless the subclass is also an
abstract class.
• The abstract method ends with semicolon.
• Example: public abstract sample();
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class Rectangle extends shape
{
void draw(){
------
}
}

33. Abstract Class
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
abstract class Media
{
protected String title;
protected float price;
media(String s, float p)
{
title = s;
price = p;
}
abstract void display();
}

34. Abstract Class
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class Book extends Media
{
protected int pgs;
Book(String s, float p, int p)
{
title = s;
price = p;
pgs = p;
}
void display ()
{
System.out.println("Title :"+ title);
System.out.println("Pages :"+ pgs);
System.out.println("Price :"+ price);
}
}

35. Abstract Class
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class Tape extends Media
{
protected int time;
Book(String s, float p, int t)
{
title = s;
price = p;
time = t;
}
void display ()
{
System.out.println("Title :"+ title);
System.out.println("Duration :"+ time);
System.out.println("Price :"+ price);
}
}

36. Abstract Class
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
class AbstractMain
{
public static void main(String args [])
{
Media book = new Book("ABC", 100, 20);
Media tape = new Tape("XYZ", 100, 20);
book.display();
tape.display();
}
}

37. Finalizer Method
• Constructor is used to initialize an object when it is declared,
process is known as initialization.
• Java supports a concept of finalization.
• JRE automatically frees up the memory recourses used y the
objects.
• But object may hold non-object resources such as window
system fonts and file descriptor.
• Garbage collector cannot be free these resources in order to
free these we must use a finalizer method.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
finalize(){
//
}

38. Interfaces: Multiple inheritance
• An interface is basically kind of class
• Like classes interfaces contains methods and
variable but with major difference
• It defines only abstract methods and final fields
• Do not specifies any code to implement these
methods and data fields contain only constants.
• Its responsibility of the class that implements an
interface to define the code for implementation
of these methods.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

39. Defining interface
interface interface-name // implicitly abstract
{
variable declaration; // implicitly public
methods declaration; // implicitly abstract, public
}
• Example:
interface Item // implicitly abstract
{
static final int code = 1001;
static final String name = “Fan”;
void display();
}
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

40. Difference between class & Interface
• Members of interface are always constant i.e. their
values are final.
• Methods in interface are abstract in nature i.e. no
code associated with it.
• An interface never be instantiated, it can only
inherited by a class.
• It can only use public access specifier.
• An interface is not extended by a class; it is
implemented by a class.
• An interface can extend multiple interfaces.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

41. Extending interfaces
interface name2 extends name1
{
//body of name2
}
• Example:
interface ItemConstants
{
static final int code = 1001;
static final String name = “Fan”;
}
interface Item extends ItemConstants
{
void display();
}
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

42. Implementing interfaces
class class-name implements interface-name
{
//body of class-name
}
• More general form:
class class-name extends super-class implements interface-name
{
//body of class-name
}
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

43. Implementing Multiple inheritance
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
Student
Test
Results
Sports
extends
extends
implements

44. Packages
• A package is a collection of similar types of classes,
interfaces and sub-packages.
• Package in java can be categorized in two form,
built-in package and user-defined package.
• Since package acts as the library which is shared by
the many people.
• Standard Java library is distributed over the number
of packages, including :
– java.lang
– java.util
– java.net and so on.
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

45. Packages
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

46. Creating packages
package mypack;// package declaration
public class class-name1
{
body of class-name
}
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

47. Using package
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).
import mypack.*;
class class-name2 extends class-name1
{
body of class-name2
}

48. Hiding Classes
Nilesh Dalvi, Lecturer@Patkar-Varde College, Goregaon(W).

49. Q & A