Introduction

Java is a platform independent object-oriented programming language developed by Sun micro systems in 1995 June. Java was designed for the development of software for consumer electronic devices like TV’s , VCR’s and other electronic devices.

Evolution

 

1990

Sun micro systems decide to develop a special software that could be used to manipulate consumer electronic devices.

1991

After exploring the possiblilty of using the most popular object oriented language c++ the team announced a new language named “Oak”

1992

The team demonstrated the application of their new language to control a list of home appliances using a hand held device with a tiny touch sensitive screen.

1993

The World Wide Web appeared on the internet and transformed the text base internet into a graphical rich environment . the green project team came up with the idea of developing web applets.

1994

The team developed a web browser called “HotJava “ to locate and run applet program on internet.

1995

Oak was renamed “JAVA” Due to some legal problems. Java is just a name and is not an acronym.

1996

Java established itself not only as leader for internet programming but also as a general purpose , object-oriented programming language. Java found it’s home.

Features

Compiled and Interpreted: Usually a computer language is either compiled or interpreted . Java combines both these approaches thus making java a two stage system. First , java compiler translate source code into what is known as byte code instructions. byte code are not machine instructions and therefore in the second stage java interpreter generates machine code that can be directly executed by the machine that is running the java program .

Platform-Independent and Portable: The most significant contribution of java over other languages is its portability . Java programs can be easily moved from one computer system to another , anywhere and anytime. Changes and upgrades in operation systems, processors and system resources will not force any changes in java programs. This is the reason why java has become a popular language for programming on internet which interconnects different kinds of systems worldwide.

Object-Oriented:  Java is a true Object-Oriented language . Almost everything in java is an object . All program code and data reside within objects and classes. Java comes with an extensive set of classes , arranged in packages, that we can use in our programs by inheritance.

Robust and Secure: java is a robust language . It provides many safeguards to ensure reliable code. It has strict compile time and run time checking for data types. It is designed as a garbage collected language relieving the programmers virually all memory management problems.      

Distributed:  Java is designed as a distributed language fo creating applications on networks. It has the ability to share both data and programs . Java applications can open and access remote objects on internet as easily as they can do in a local system.

Simple, Small and Familiar:  Java is a small and simple language. Many feature of C and C++ that are either redundant or sources of unreliable code are not part of java.. Java does not use pointers preprocessor header files, goto statement and many others .

Multithreaded and Interactive:  Multithreaded means handling multiple tasks simultaneously. Java supports , multithreaded programs . This means that we need not wait for the application to finish one task before beginning another. for example we can listen audio clip while scrolling a page.

High Peroformance:  Java performance is impressive for an interpreted language . mainly due to the use of intermediate bytecode. according to sun, java speed is comparable to the native C/C++ . Java architecture is also designed to reduce overheads during runtime further.

Dynamic and Extensible: Java is dynamic language . Java is capable of dynamically linking in new class libraries, methods, and objects. Java can also determine the type of class through a query , making it possible to either dynamically link or abort the program depending on the reponse. Java programs support functions written in other languages such as C and C++. These functions are known as native methods. this facility enables the programmers to use the efficient functions available in these languages. Native methods are linked dynamically at runtime.

Java and Internet
                Java is strongly associated with the internet because of the fact that the first appplicaton program written in java was HotJava , a web browser to run applets on internet. Internet users can use java to create applet programs and run them locally using a java enabled browser such as hotjava.
Java and World Wide Web

                World Wide Web is an open-ended information retrieval system designed to be used in the internet’s distributed environment. this system contains what are known as web pages that provide both information and controls .

Machine neutral
               
The compiler converts the source code files into bytecode files. these codes are machine independent and therefore cab be run on any machine . that is , a program compiled on IBM machine will run on a macintosh machine.
Java intereter reads the bytecode files and translates them into machine code for the specific machine on which the java program is running . the interpreter is therefore specially written for each type of machine.

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