basic of java-language

7/31/2019 Basic of JAVA-Language

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INTRODUCTION to JAVA Java was conceived by James Gosling, Patrick

Naughton, Chris Warth, Ed Frank, and MikeSheridan at Sun Microsystems, Inc. in 1991name with Oak

In 1992 this can be used in hand held devices

1993 this cab be used in WWW applications

the same team in 1994 Hotjava bower isdeveloped ,it is more popular internet users.

This language was initially called Oak but wasrenamed Java in 1995

1996 java itself established not only internet

program but also general purpose, and OOPlanguages.


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The Bytecode

Bytecode is a highly optimized set ofinstructions designed to be executedby the Java run-time system, which is

called theJava Virtual Machine (JVM). That is, in its standard form, the JVM

is an interpreter for bytecode. This

may come as a bit ofa surprise


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Java Features

Simple Secure

Portable

Object-oriented

Robust

Multithreaded Architecture-neutral

Interpreted

Hi h erformance


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SimpleJava is simple because there are

various features that makes the java

as a simple language. Programs are

easy to write and debug because

java does not use the pointers

explicitly, operator overloading ,multiple inheritance, process header

files, goto stement


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Object-OrientedTo be an Object Oriented language, any

language must follow at least the four

characteristics.

Inheritance

Encapsulation

Polymorphism

Dynamic binding

R


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Ro ust

Java is a strictly typed language, it

checks your code at compile time.

Java has the strong memory

allocation and automatic garbage

collection mechanism.

It provides the powerful exception

handling and type checking


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Multithreaded Multi thread means handling multiple

tasks simultaneously

Java supports multithreaded

programming, which allows you to

write programs that do many things

simultaneously.

Java is also a Multithreaded

programming language.


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Architecture-Neutral One of the main problems facing

programmers is that no guaranteeexists that if you write a programtoday, it will run tomorroweven on

the same machine Operating system upgrades,

processor upgrades, and changes in

core system resources can allcombine to make a programmalfunction


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The Java compiler does this by

generating byte code instructions, to

be easily interpreted on any machine

and to be easily translated intonative machine code

The compiler generates an

architecture-neutral object file format


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Interpreted and HighPerformance

Java enables the creation ofcross-platform programs by compiling intoan intermediate representation called

Java bytecode. This code can beinterpreted on any system thatprovides a Java Virtual Machine

Other interpreted systems, such asBASIC, Tcl, and PERL, suffer fromalmost insoluble performance deficits.

Java, however, was designed to-


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Distributed

Java is designed for the distributedenvironment of the Internet, becauseit handles TCP/IP protocols, HTTP and

FTP are developed in java In fact, accessing a resource using a

URL is not much different from

accessing a file. Internet programmers can call

functions on these protocols and can

get access the files from any remote
http://www.roseindia.net/java/java-introduction/java-features.shtmlhttp://www.roseindia.net/java/java-introduction/java-features.shtml


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Dynamic Dynamic Java programs carry with

them substantial amounts of run-time type information that is used toverify and resolve accesses to

objects at run time.This makes it possible to dynamically

link code in a safe and expedient

manner.Java is capable of dynamically linking

in new class libries, methods and

objects.


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Portability

The feature Write-once-run-anywhere makes the javalanguage portable provided that the system must haveinterpreter for the JVM.

programs to be dynamically downloaded

to all the various types of platformsconnected to the Internet, some means ofgenerating portable executable code isneeded.

the same mechanism that helps ensuresecurity also helps create portability


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Security

Java system verify all memory accessbut also ensure that no virus are

communicated with appletJava achieves this protection by

confining a Java program to the Java

execution environment and notallowing it access to other parts of thecomputer.

The absence of pointers that


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Java environment

JDK (java development KIT)collection of tools

Appletviewer ( java compatiblebrowser)

Javac ( compiler)

Java (interpreter)Javap( dis assembler) : convert the

bytcode to program

Javah : produces the header files for


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JAVA API Language support package

Utilities package

Input /Out package

Networking package AWT package

Applet package


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Data Types, Variables,and Arrays

Integers This group includes byte,short, int, and long, which are forwhole valued signed numbers.

Floating-point numbersThis groupincludes float and double, whichrepresent numbers with fractional

precision.

Characters This group includes char,which represents symbols in a

character set, like letters and numbers.


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Integers

long 64 9,223,372,036,854,775,808 to

9,223,372,036,854,775,807

int 32 2,147,483,648 to2,147,483,647

short 16 32,768 to 32,767

byte 8 128 to 127


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Floating-Point Types

Double 64 4.9e324 to1.8e+308

float 32 1.4e045 to 3.4e+038

Literals

Integer Literals

Floating-Point Literals

Boolean Literals

Ch t E


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Character EscapeSequences

Escape Sequence Description \ddd Octal character (ddd)

\uxxxx Hexadecimal UNICODE

character (xxxx) \ Single quote

\ Double quote

\\ Backslash

\r Carriage return

\n New line (also known as line


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VariablesThe variable is the basic unit of

storage in a Java program. A variableis defined by the combination of anidentifier, a type, and an optional

initializer. In addition, all variables have a

scope, which defines their visibility,

and a lifetime Declaring a Variable

type identifier[ = value][, identifier [=

value] ...] ;


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Arrays

One-Dimensional Arrays type var-name[ ];

int month_days[];

int month_days[] = { 31, 28, 31, 30,31, 30, 31, 31, 30, 31, 30, 31 };

Multidimensional Arrays

int twoD[][] = new int[4][5];


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Sample program

/*

This is a simple Java program.

Call this file "Example.java". */

import java.io.*;

import java.util.*;

class Example {

// Your program begins with a call to


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Progrm-ii

import java.io.*;

import java.util.*;

class Example2 {

public static void main(String args[]) {

int num; // this declares a variablecalled num

num = 100; // this assigns num the

value 100


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Using arrays

class Average {

public static void main(String args[]){

double nums[] = {10.1, 11.2, 12.3,13.4, 14.5};

double result = 0; int i;

for(i=0; i


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Two dimensional arrays

class TwoDArray {

public static voidmain(String args[]) {

int twoD[][]= newint[4][5];


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