Welcome to Java. 2 History of java Advantages of java Java first program Rules to be followed Data types Operators Casting Control statements.

Welcome to Java

History of javaAdvantages of javaJava first programRules to be followedData typesOperatorsCastingControl statementsTaking input from

keyboard

ArraysStringsString buffer and string

builderOops conceptsAccess specifiersConstructorsDifferent types of

methodsThis Keyword

contents

Contents continued

Interface and package

ThreadsException handlingGraphical

programmingAwtSwingsApplet

This is java tutorial from Java Bean this is the demo version of first class

In this tutorial we are going to learn the basic foundations required to learn java

Before getting into java the first question comes to mind is

Is java tough ?

5

Definitely not !

If yes then how we understand other languages like English, Hindi although our mother tongue may be different how we learnt those languages

We had certain basic foundation through which we Started learning

We started with alphabets A B C D grouped these alphabets to form words .we grouped these words to form sentence

These sentences are used as communication bridge to talk and understand others talk

Similarly we can learn java .here also we have alphabets known as variables, words known as keywords statements known as syntax

By using these syntax we can communicate to computer to perform task

English Java

Alphabets variables

Words Keywords

Statements Syntax

Before stepping into java ,basic knowledge of C& C++ is needed as they are the foundation on which java is been designed

If you don’t have no need to worry in this tutorial required knowledge of C & C++ is covered

Let us begin Java with C program….hello word to know the meaning of Syntax(So called statements)

#include<stdio.h>

main() {

printf("Hello World"); }

Simple Hello world Program

# means preprocessor directives

As a name says which are processed before , The C preprocessor modifies a source file before handing it over to the compiler

Or we can say pre written,

Include is simple including of pre written function definition

<stdio.h> is a label where the definition of function are Stored

Don’t be confused now we will understand where #include<stdio.h> will come into picture

In last slide I was talking about function definition

Basically there are 2 types of functions 1.Predefined 2.Userdefined

Function is defined as set(group) of syntax performing specific task

Basically function as two partsFunction prototype(head)Function body(defination)

add()…………………….function prototype(head){………….………………….}

Function body

function prototype: Says what I am going to do

function definition: Says what task I am doing

When we consider our above program we have to functions

main()

printf()

#include<stdio.h>

main()……………………..no semicolon {

printf("Hello World"); …….semicolon }

What difference you can notice between main and printf

When function has no semicolon it is followed by { and ended with }Which means head and body exist

Main : is the function where execution starts

After main exection goes to printf(); where no defination is found so compiler goes to library search for <stdio.h> label inside which it search for printf defination

When defination is found it copies the entire code from library to program and execute it

add()…………………….function prototype(head){………….………………….}

Function can only executed if it has both head and body

Then in case of printf(); where is the body,if no body how can it run

Function body

Regular used functions definition are pre written and are stored in library which at the start of the program we are including

Since there are lot of predefined functions they categorized by labels<stdio.h><conio.h><math.h>

In these blocks respective function definitions are stored

Similarly the function defined by us are called as user defined function

#include<stdio.h>

main() {

printf("Hello World");

}

C library

Stdio.h Conio.h

Math.h

definition

The reason to start with c program was just to know the meaning Of the words what we use in program , when we know the meaning of the syntax,programs are easy to learn

now it’s a time to know how java came into existence and why it has become so important

Although we have c and c++ ,why java came into existance ?

Where c and c++ fail……..?

C and C++ failed due to platform dependencies

Platform is base where we run program, platform is combination of operating System and Processor

Win 7os

keyboard

I3process

or

platform

When we write C program in operating system and processor ,it can be re runned in only in same operating system and processor

For example if I write program in win7 nd p4 processor it can be runned again in the same,if I try to run in different os and processor like win7 and i5 ,it fails to run

Why c and c++ fail to run…?

case 1

Win7P4

Add.c

case 2

Win7I3

Add.c

Add.obj Add.obj

Add.exe Add.exe

Compile

run

Compile

run

Why it is not running…………?

Lets know the reason

When we write c program we save with the extension .cAdd.c

This is source code

When we compile c program we get the extension .objAdd.obj

This is machine code(object code)

This machine code always depends upon processor and operating System

case 1

Win7P4

Add.c

Add.obj

Add.exe

Compile

run

Let us consider Case 1Os:-win 7Process:p4

When we compiles Add.cFor adding of two numbers Machine codeformat we get

Add A,B

case 2

Win7I3

Add.c

Add.obj

Add.exe

Compile

run

When we consider case 2Os:win7Process:i3

When we compiles Add.cFor adding of two numbers Machine codeformat we get

A ADD B

Now we try to take code of case 1 after compiling and pate to run in case 2Case 1 lang:ADD A,B

Case 2 lang:A ADD B

Case 2 cannot recognize case 1 language hence it cannot run

This made c and c++ failure

Since all systems cannot have same os and processor it is platform dependent

Being a software developer we want our application(program) to be used by all in such a case it should be recognized by all the system

This made the invention of java

History of java

Gosling is founder of Java programming language in 1994 it was named as oak

In January 1995 it was renamed as java since was already registered

Its platform independent pure object oriented if we write once we can run anywhere

Import java.io.*public class HelloWorld { public static void main(String[] args) { System.out.println("Hello, World"); }}

Simple java Program

Before we enter in depth lets see how it was made platform Independent

Saving java program:Example.java

After compiling

Example.class

Class code is not machine code like c,it is called as Byte code

Byte code is a intermediate code which is nither source code nor machine code

Problem was machine code reason if we convert to Machine code only that machine can understand

This code is given to converter (jvm) which converts to machine language depending on machineHence depending on machines there are flavors of jvm

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Let us consider example

Person AKnows only

english

Person BKnows

english/french

Person cKnows only

French

Similar Thing happens in java

This is how java is platform independent

jvm

jvm

jvm

Advantages of javaJava first programRules to be

followed

This is it For First class We shall continue next class with below topics