Introduction of JAVA

 

INTRODUCTION 

OF

 JAVA 

š JAVA:

Java is developed by James A. Gosling. It is an object oriented programming language. Earlier this language was called ‘OAK’. It is a very popular programming language of III^rd generation. It can perform various tasks as others programming languages including internet and intranet. This language also helps to manage networks. It can be treated as a platform to various applications.

 

š JAVA Environment :

It includes a large number of development tools, number of classes and functions / methods. The development tools are part of the system known as JAVA DEVELOPMENT KIT (JDK). The classes and methods are the part of JAVA STANDARD LIBRARY (JSL), also known as APPLICATION PROGRAMMING INTERFACE (API).

š JAVA DEVELOPMENT KIT (JDK) TOOLS :

S. No.	Tools	Description	Purpose
1	javac	Java Compiler	Translates java source code to byte code files to make them understandable by the interpreter.
2	java	Java Interpreter	Runs applets and applications by reading and interpreting byte code files
3	jdb	Java Debugger	Helps in finding errors in the current program.
4	applet viewer	To see Java Applets	Helps in running the java applets without using java compatible browser.
5	javap	Java Disassembler	Helps in converting byte code files into a program description.
6	javah	For C header file	Includes header files for use with native function / method.
7	Javadoc	Create HTML documents	Helps in creating HTML format documentation for java source code files.

š Basic Features Of JAVA :

The basic features of Java are as follows:

1.      The programs can be compiled and interpreted.

      2.      It is a platform independent language.

      3.      It is a robust programming language.

      4.      It is a multi-threaded language.

      5.      It can access data from a local system as well as from net.

      6.      Java programming is written within a class.

      7.      Java can create applets.

      8.      It is a case sensitive language.

      9.      It does not require any preprocessor (#) for running application program.

     10.  It is 3^rd generation programming language.

           

š Characteristics of JAVA :

 The characteristics of java are as follows:-

1.      Light weight code.

2.      Supports multimedia.

3.      Open Product.

4.      Security.

5.      Built in graphics.

6.      Write Once Run Anywhere (WORA).

7.      Platform independent.

8.      Object Oriented Language.

 

š Disadvantages of JAVA:

 The following are the disadvantages of Java are as follows:

1.      No local constants: In java, variables that belong to a class can be made constant by declaring them to ‘final’. Variables that are local to a method cannot be declared final.

                  2.      Exceptions cannot be caught within the method must be declared as thrown by that 

                        method.

                  3.      Every user computer must have JVM installed to run application successfully.

 

     š Compiler:

It compiles the whole program in one go and generates the list of errors.

š Interpreter : 

It debugs the program line – by – line and if any line contains errors then first   

          rectify the error and  then again interpreting from the first line.

 

š Java Byte Code:-

The java byte code is machine instruction for a java processor chip called java virtual machine (JVM). The byte code is independent of the computer system it has to run upon.

 

š Java Virtual Machine (JVM) :

When java program is compiled to its intermediary code called byte code. When this byte code is run on any system, an interpreter (JVM) is needed to translate the byte code to machine code.

                         JVM acts as virtual processor, which processes the byes code to machine code instructions for various platforms. That’s why it is known as JAVA VIRTUAL MACHINE (JVM).

 

š Ordinary Compilation Process :

                   In this, source is converted to a machine code which is dependent upon machine or the platform. The resultant code is called native executable code

 

š JAVA Compilation Process :

             In this, java compiler produces byte code and it looks like a machine language, but unlike machine java byte code is exactly the same for every platform. Then this java byte code translates into machine code with the help of JVM.

 

š Types of Java Programs :

o    STAND ALONE APPLICATIONS (JAVA APPLICATIONS): A java program, which is developed by the user, is termed as java application or stand alone applications.

o   INTERNET APPLETS : These are the small programs that are embedded in web pages and are run on the viewer’s machine in a secured manner by java capable browsers.

§  JAVA Libraries :

The java development kit contains java libraries for different purposes. Some libraries are as follows : java.lang, java.io, java.applet, java.net, java.awt, java.txt, java.math.