Java introduction

1. JAVA
SUJIT MAJETY | 1 : INTRODUCTION TO JAVA

2. Course Description

Introduction to JAVA

Location : SREC

History

Lectures: Weekdays at 11:00 am

Features

Labs: Weekdays at 01:30 pm

JVM

Presenter:

Architecture of JVM

Introduction to OOPS

Object

Class
Sujit Majety,
Software Engineer,
Tech Fort IT Solutions (INDIA) PVT Ltd.

3. Introduction to JAVA

Let’s start the exiting journey.

Java is one of the most powerful programming languages.

Java is Cross-platform, object-oriented, network-based, reliable programming
language.

The slogan of java is “write once and run anywhere”, this allowed java to gain
enormous popularity. Its rapid ascensation and wide acceptance can be traced to its
design and programming features.

The name “JAVA” came from the name of the coffee seed.

JAVA released to market in three versions J2SE, J2EE, J2ME

4. Programming Paradigm
Procedure Oriented

More emphasis on algorithms.

Programs divided into functions.

Most functions share data, less security to
data.

Data move around the system between
functions, any function can change the data.

Adding new code is very difficult.

Code cannot be re-used.

E.g. C, VB, Perl, Basic, Fortran
Object Oriented

More emphasis on data.

Programs are divided into objects.

Functions operate on data are tied together
in the data structure.

Data is secured; it is hidden to external
functions, can be accessed by functions
tied to it.

Adding new code is very easy.

Code can be re-used.

E.g. CPP, Java, VB.Net, C#.Net

5. History

Developed by a team led by James Gosling at Sun Microsystems.

Sun Microsystems was a company best known for its workstations.

Java was originally OAK, designed for use in embedded consumer electronic
application in 1991.

OAK was redesigned for developing internet applications and renamed JAVA in
1995.

Java is inherently object-oriented.

6. Features
There are eleven promising features in java

Simple (no pointers, interfaces, rich set of API, friendly syntaxes)

Secure (many number of security mechanisms to block stray programs)

Portable (can run on any operating system)

Robust (memory management, exceptional handling)

Distributed (runs on multiple servers and can be accessed by no of clients)

Interpreted (both compiled and interpreted)

Multi Threading (multiple flow of controls)

Dynamic (is always open for updating)

Architecture Neutral (can run on any processor)

High Performance (garbage collector, leaves resources wile waiting for inputs)

Object oriented (everything is written in class)

7. Java Virtual Machine

JVM is an abstract machine.

It is a specification that provides runtime environment in which java byte code can be
executed.

JVM’s are available for many hardware and software platforms (i.e. JVM is platform
dependant).

JVM performs four main tasks,

Loads code

Verifies code

Executes code

Provides runtime environment.

8. Architecture of JVM
Class Loader
Subsystem
Class Files
Runtime
data
areas
Method
Area
Execution Engine
Heap
Stack
PC
Registers
Native
Method
Area

9. Introduction to OOPS

Object oriented programming models the real world.

Object oriented programming organizes a program around its data and set of well
defined interfaces to that data.

An object-oriented program can be characterized as data controlling access to
code.

By switching the controlling entity to data, you can achieve several organizational
benefits.

Object oriented programming, the first letter indicates object.

What is an object?

10. Object

An object is the basic unit of object orientation with behaviour and identity.

An object is a real time entity. E.g.. Car, bike, book, me and you.

It is a runtime entity that has a state and behaviour.

The state of the object represents the data.

The behaviour is represented by the methods.

E.g. An object is created to represent a rabbit.
It would have data: how hungry it is, where it is.
And methods : eat, hide, run and dig.

11. Class

A class is a way of binding the data and associated methods into a single unit.

A class can also be said as a blue print to create an object.

If we want to develop a java program, then that should be developed with respective of
class only. i.e. without class there is no java program.

Syntax:
Class <clsname>
{
Variable declaration;
Class Name
Animal
Data members/
properties/
Attributes
Name,
Number of legs,
Colour
Behaviours/
Methods
Eat(),
Walk(),
Sleep()
Methods definition;
};

12. Sample Program
class Test
{
public static void main(String[] args)
{
System.out.println(“Hello World”);
}
}
Execution:
> javac Test.java
> java Test

13. Execution of java program

The java program execution can be seen through the following
figure.
Test.java
Test.class
JVM
Java Program
Source code
Byte code
JVM converts byte
code to m/c code
Console
Program Output

14. Important Interview Questions

What is the most widely used protocol on internet

What is the difference between an executable file and .class file?

Why java is suitable for internet?

Why pointers are eliminated in java?

What is the difference between a function and a method?

Which part of the JVM will allocate the memory for java program?

Which algorithm is used by garbage collector to remove the unused variables or objects
from memory?

15. Assignments

Check the hello world program by removing each and every word.

Shuffle the order of public static void main

Try experimenting with print & println.

Try giving different names for args.

Try giving int args[] instead of String args[] in main.

Give Different name for the filename and the class name

Repeat the above problem with declaring class as public

Copy the class file into different folder name and execute it.

Write your own program, compile it and execute it.

Try giving different data types ( the one you know like int x, double d ) in the prinltn and see if it prints all of
them.

I have two Integers int x =1; and int x=2; I wish to print 12. find the ways to print.

Repeat the same if I want to print given int x=1; double d=2.5; and print 12 instead of 12.5

16. Questions?

17. Sujit Majety
+91 9000019878
mail to : sujit.naga@gmail.com