java programming

TRINITY INSTITUTE OF PROFESSIONAL STUDIESSector – 9, Dwarka Institutional Area, New Delhi-75

Affiliated to Institution of G.G.S.IP.U, Delhi

BCA

Java Programming

20206

Ms. Bharti DewaniAssistant Professor


What is Java?

A simple, object oriented, distributed, interpreted, robust, secure, architecture neutral, portable, high performance, multithreaded, dynamic language.

From: Java: An Overview

James Gosling, Sun Microsystems, February 1995.


Why Java?

• Java is a general-purpose, high-level programming language.

• It’s almost entirely object-oriented• It has a vast library of predefined objects and

operations called The Java Application Programming Interface OR JAVA API

• It’s more platform independent– this makes it great for Web programming

• It’s more secure• It’s a software-only platform running on top of other,

hardware-based platforms.


Features of Java

• Simple

• Architecture-neutral

• Object-Oriented

• Distributed

• Compiled

• Interpreted

• Write once, run anywhere

• Statically Typed

• Multi-Threaded


Features of Java (Contd.)

• Portable

• High-Performance

• Robust

• Secure

• Extensible

• Well-Understood

• Garbage Collected

That’s why they say …

“ Java has changed programmer’s life . ”


Java Applications and Java … lets

• Stand-alone Applications

– Just like any programming language

• Applet

– Run under a Java-Enabled Browser

• Midlet

– Run in a Java-Enabled Mobile Phone

• Servlet

– Run on a Java-Enabled Web Server


Java Developer's Kit

• Java's programming environment

– Core Java API

– compiler

– interpreter

– debugger

– dis-assembler

– profiler


Java Developer's Kit (Contd.)

Java source(.java)--java compiler-->java bytecode(.class)

Java bytecode(.class)--java dis-assembler-->java source

Java bytecode--java interpreter-->machine code (O/P)


Java API

• Collection of ready-made i.e pre-defined software components that provide many useful capabilities.

• Grouped into libraries , packages of related components i.e collection of inter-related or similar classes and interfaces


Core API

– Essentials: Object, String, Input and Output...– Applets– Networking– Internationalization– Security– Software Components– Object Serialization– Java Database Connectivity (JDBC)


Building Standalone JAVA Programs (on UNIX)

The “Hello World” application


Create a Java Source File

• Pepare the file HelloWorld.java using an editor

public class HelloWorld {public static void main(String[] args) {System.out.println("Hello World!");} }

• Since Java is object-oriented, programs are organized into modules called classes, which may have data in variables and subroutines called methods.

• Note that String is built-in and• println is a member function for the System.out class


Compile and Run

• Compile

– javac HelloWorld.java

• A file named HelloWorld.class is created if the compilation succeeds.

• Run

– java HelloWorld

Output:- Hello World!


Comparing Java with C , C++


Java and C++

Comments are almost like C++• /* This kind of comment can span multiple lines

*/

• // This kind is to the end of the line

• /**

* This kind of comment is a special

* ‘javadoc’ style comment

*/


Java and C

Primitive data types are like C• Main data types are int, double, boolean, char

• Also have byte, short, long, float

• boolean has values true and false

• Declarations look like C, for example,

– double x, y;

– int count = 0;


Java and C

Control statements are like C• if (x < y) smaller = x;

• if (x < y){ smaller=x;sum += x;}

else { smaller = y; sum += y; }

• while (x < y) { y = y - x; }

• do { y = y - x; } while (x < y)

• for (int i = 0; i < max; i++) sum += i;

• BUT: conditions must be boolean !


Java Vs. C

• C is procedural whereas Java is object oriented.

• In C, almost everything is in functions

• In Java, almost everything is in classes

• There must be only one public class per file

• The file name must be the same as the name of that public class, but with a .java extension

• In Java, there is nothing called Pointers


Java Vs. C++

• In Java,no preprocessor directives required

• In Java, header files are not included but Predefined classes and interfaces can be imported to achieve Reusability.

• Destructor() method is replaced by finalize() method

• Only two contructors viz. default and parameterisedare allowed in java

• Multiple inheritence is achieved via a new concept called interface


Thank you..

java programming

Internet

java interpreter

java compiler

java applications

java source java bytecode

new delhi

delhi bca java programming

dwarka institutional

class java bytecode