Java-Intro.pptx

Object Oriented
Programming with JAVA

Syllabus
1. Introduction to Object Oriented Programming
2. Class, Object, Packages and Input/Output
3. Array, String and Vector
4. Inheritance
5. Exception handling and Multithreading
6. GUI programming in JAVA

Books
Textbook
• E. Balagurusamy, ‘Programming with Java’, McGraw Hill Education.
• Herbert Schildt, ‘JAVA: The Complete Reference’, Ninth Edition, Oracle
Press.

Introduction to Object Oriented Programming
• OOP concepts: objects, class, encapsulation, abstraction, inheritance,
polymorphism, message passing
• Java Virtual Machine
• Basic programming constructs: variables, data types, operators,
unsigned right shift operator, expressions, branching and looping.

Object Oriented Programming concepts

Classes & Objects
• The class is the unit of programming
• Class – user-defined datatype
• A Java program is a collection of classes
• Each class definition (usually) in its own .java file
• The file name must match the class name
• A class describes objects (instances)
• Describes their common characteristics: is a blueprint
• Thus all the instances have these same characteristics
• These characteristics are:
• Data fields for each object
• Methods (operations) that do work on the objects

Encapsulation:
• wrapping up of data under a single unit
• the variables or data of a class is hidden from any other class and can
be accessed only through any member function of own class in which
they are declared.
Abstraction:
• by virtue of which only the essential details are displayed to the user
• Eg: man driving a car, only knows how to apply a break, does not
need to know mechanism behind it.

Inheritance
• one class can inherit the features(fields and methods) of another
class.
• Facilitates reusability

Polymorphism
• Ability to differentiate between entities with the same name
efficiently.
• This is done by Java with the help of the signature and declaration of
these entities.
• Eg: addition operation of integer and strings
Dynamic binding
• Process of linking a method call to the executable code in response to
the call
• This process exhibited at runtime

Message Communication
• Objects Communicate with each other
Steps:
1. Create classes that define objects
2. Create objects from class definitions
3. Establish communication among objects
Eg:
Car c;
c.speed(c);

Features of JAVA
Compiled & Interpreted
• Two stage system
• Compiler – source code into bytecode
• Interpreter – bytecode into machine instructions
Platform independent & portable
• Programs can be easily moved from one computer system to another,
anywhere & anytime.
• Ensures portability in two ways:
• Generates bytecode instructions, which can be implemented anywhere
• Size of primitive data type is machine independent

Features of JAVA
Object-Oriented
• All the Code of the java Language is written into the classes and
objects
Robust & Secure
Robust
• Eradicates the problem of memory management by performing
automatic garbage collection
Secure
• Absence of pointers ensures that programs cannot gain access to
memory locations without proper authorization

Features of JAVA
Distributed
• Program of java is compiled onto one machine can be easily
transferred to machine and executes them on another machine
• Used to create applications on network
Simple, small & familiar
• Java removes complexity because it doesn’t use pointers, storage
classes and go to statements and java doesn’t support multiple
inheritance
Multithreaded & Interactive
High Performance

JDK, JRE & JVM
• JDK is platform specific software
• JRE provides platform to execute Java
program
• JVM Provides runtime environment in
which java bytecode can be executed
• JVM is available for many hardware and
software platforms (i.e. JVM is platform
dependent).

Let’s Begin Programming
class Sample //Sample Program
{
public static void main(String args[])
{
System.out.println(“Hello World!!!”);
}
}
//System class is defined in java.lang.* (default imported package)
//static – interpreter uses this method before any objects are created
/*….Multi line comment */
Identifier
Keyword
Class
Object
Method
Access
Specifier

Implementation?
Creating the program
• Using any text editor (known as source file)
• Save the file
Compiling the program
• javac filename.java //creates bytecodes file (filename.class)
Running the program
• java filename //interpreter looks for the main method

Variables
• Name given to a memory location; all the operations done on the variable
effects that memory location
• Value stored in a variable can be changed during program execution
Rules:
1. Should not begin with digit
2. Case sensitive
3. Should not be a keyword
4. White space is not allowed
5. Can be of any length
Eg: total_value, mean

Constants
• Variable whose value cannot
change once it has been
assigned
Syntax:
final float pi=3.14;
• Variables as constants by just
adding the keyword “final”
when we declare the
variable.

Special operators
instanceof operator
• Returns true if the object on the LHS is an instance of the class given
on RHS
eg: person instanceof Student
Dot (.) operator
• Used to access the instance variables & methods of class objects
eg:
person.age
person.salary()

Java Math methods
• java.lang.Math class contains various methods for performing basic
numeric operations such as the logarithm, cube root, and
trigonometric functions etc.
Method Description Arguments
abs Returns the absolute value
of the argument
Double, float, int, long
round Returns the closed int or
long (as per the argument)
double or float
ceil Returns the smallest
integer that is greater than
or equal to the argument
Double
floor Returns the largest integer
that is less than or equal to
the argument
Double
min Returns the smallest of the
two arguments
max Returns the largest of the
two arguments
Sin Returns the Sine of the
specified argument
Double
Cos Returns the Cosine of the
specified argument
double
Tan Returns the Tangent of
the specified argument
Double
Atan2 Converts rectangular
coordinates (x, y) to
polar(r, theta) and returns
theta
Double
toDegrees Converts the arguments
to degrees
Double
Sqrt Returns the square root of
the argument
Double
toRadians Converts the arguments
to radians
Double

Java Math methods
exp Returns the base of
natural log (e) to the
power of argument
Double
Log Returns the natural
log of the argument
double
Pow Takes 2 arguments as
input and returns the
value of the first
argument raised to
the power of the
second argument
Double
floor Returns the largest
integer that is less
than or equal to the
argument
Double
Sqrt Returns the square
root of the argument
Double

Command line argument program
class Arguments
{
{
System.out.println("Arguments are");
for(int i=0;i<args.length;i++)
System.out.println(args[i]);
}
}
Note:
Converting string to integer
Integer.parseInt(args[0])

Multiple classes
class Room
{
float length, breadth;
void getData(float a, float b)
{
length=a;
breadth=b;
}
}
class RoomArea
{
{
float area;
Room r=new Room();
r.getData(4,5);
area=r.length*r.breadth;
System.out.println(“Area of a room is:”+area);
}
}

Input
Package: java.io
I/P statement:
BufferedReader br=new BufferedReader(new InputStreamReader(System.in))
Create a
object &
allocates
memory
dynamically
Class can be
used to read
data from
keyboard
Class can be
used to read
data line by
line
Input stream
which is
typically
connected to
keyboard for
input

import java.io.*;
class Test
{
public static void main(String args[])throws IOException
{
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
System.out.println(“Enter your name”);
String name=br.readLine();
System.out.println(“Welcome: ”+name);
}
}
// return type of readLine() is String
Integer.parseInt(br.readLine()); //String to integer

Scanner class Input
import java.util.Scanner; // Import the Scanner class
class MyClass
{
{
Scanner myObj = new Scanner(System.in);
System.out.println("Enter username");
String userName = myObj.nextLine();
System.out.println("Username is: " + userName);
}
}
// return type of nextLine() is String
Integer.valueOf(myObj.nextLine()); //String to integer

Scanner class Limitation
import java.util.Scanner;
class Input
{
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.print("Enter flight number: ");
int flightNumber1 = scanner.nextInt();
System.out.print("Enter flight2: ");
System.out.print("Enter departing city");
String departingCity = scanner.nextLine();
System.out.print("Enter arrival city: ");
String arrivalCity = scanner.nextLine();
}
}

Workaround
import java.util.Scanner;
class Input1 {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
System.out.println("Enter flight number1: ");
scanner.nextLine();
System.out.println("Enter departing city:");
System.out.print("Enter departing city");
System.out.print("Enter arrival city: ");
String arrivalCity = scanner.nextLine();
}
}

If-else example
public class IfElse
{
{
int n=7;
if(n%2==0)
System.out.print(“Even”);
else
System.out.print(“Odd”);
}
}

Switch example
class SwitchDay
{
{
int day=7;
switch(day)
{
case 1:
System.out.println(“Monday”);
break;
case 2:
System.out.println(“Tuesday”);
break;
case 3:
System.out.println(“Wednesday”);
break;
case 4 :
System.out.println(“Thursday”);
break;
case 5:
System.out.println(“Friday”);
break;
case 6 :
System.out.println(“Saturday”);
break;
case 7 :
System.out.println(“Sunday”);
break;
}
}
}

Loops
For loop While loop
• WAP to print all even integers
divisible by 6 or 7 upto 50
Do while loop
• WAP to print 10 to 20

Java-Intro.pptx

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