Java Introduction

JAVA CHARACTERSITICS
Sun Micro Systems introduced java in 1995 and its cofounder Bill Joy described java as follows.
Java is just a small,simple,safe,object-oriented,interpreted,byte-coded,architecture,neutral.garbage-collected,multithreaded and strongly typed with exception-handling mechanism.
Let us understand Java characteristics little in detail:
Architecture neutral: Java file can run on any cpu architecture ie. It may be Intel ,Motorola or AMD.etc.
Platform –independent:java developed under any operating system can run on every operating system.One leading bank has replaced 80 million lines of plat- form specific banking applications with 20 million lines of java code.What a saving!
Object oriented fully:All program tokens have to be included in classes ,even main() function.In java programming,derived classes cannot have more than one super class ie.multiple in heritance is not supported.
Byte-coded:Java is compiled and interpreted language.Source code is first compiled similar to machine code but can be executed on any operating system wich has java interpreter.The interpreter reads the byt-ecode file and translates into machine language which can be directly executed by the local machine where java program is running.
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(1)Java pointers can be used to forge access to that part of program where access is not allowed and to access areas in memory that are supposed to be unalterable. So pointers are not supported in java.
(2)Byte code verifier: Before a java program is run,a verifier checks each byte code to make sure and assures that no viruses are there with a running applet.
Extensible: Java supports native methods written in another language,usually c++.
Multi-threaded: Java supports multiple path of execution in a program so that several tasks like rendering an image on the screen on one thread and accepting key board in put in the main thread can run simultaneously.
Exception handling mechanism:When any serious error is encountered,java creates an exception.This exception can be captured and managed by the program without system crashing.Java has its own garbage collection mechanism.User need not required to delete objects when they go out of their scope .So java is robust.
RMI supported:Java is suitable for distributed computing by providing tools for managing Remote Method Invocation .
Internet compatible: Java is net centric. Its networkability separates java from other languages.Many tell it is the language of Internet. Java applets helps to distribute executable components on Internet providing user interaction.
Flow chart for executing java programs

There are some features,whch Jav programming does not support but C++suppots:
1. Java does not support Pointers.
2. No implicit type casting.
3. No structures and unions.
4. No operator overloading .
5. No templates , header files.
6. Doesnot support multiple inheritance.