TOOLS OF JAVA

 VARIOUS TOOLS AVAILABLE IN JAVA, WHICH MAKES IT RUN ON ANY MACHINES. THEY ARE:

JAVAC (COMPILER):- IT IS USED TO CONVERT JAVA PROGRAM INTO CLASS FILE WHICH CONTAINS BYTE CODES.

JAVA (INTERPRETER) :- IT IS USED TO EXECUTE CLASS FILE MEANS BYTE CODES.

JAVAP (PROFILER COMPILER) :- IT IS USED TO CONVERT CLASS FILE INTO JAVA PROGRAM. IT GIVES ONLY STRUCTURE OF THE JAVA PROGRAM. IF WE USE "JAD" UTILITY WE GET ENTIRE JAVA PROGRAM FROM CLASS FILE.

JAVAH (HEADER FILE COMPILER) :- IT IS USED TO INCLUDE NATIVE METHODS, HEADER FILES INTO JAVA PROGRAM.

JAVADOC (DOCUMENTATION COMPILER) :- IT IS USED TO CONVERT JAVA PROGRAM INTO HTML DOCUMENT. THE GENERATED HTML DOCUMENT IS CALLED API DOCUMENT.

APPLETVIEWER :- IT IS USED TO EXECUTE APPLETS (SMALL WEB PROGRAMS).

METHOD :- SET OF STATEMENTS.

CLASS / INTERFACE :- SET OF METHODS.

PACKAGE :- SET OF CLASSES & INTERFACES.

JSL (JAVA STANDARD LIBRARY) :- SET OF PACKAGES.

JRE (JAVA RUNTIME ENVIRONMENT) : JVM + JSL.

          TYPES OF JAVA APPLICAIONS
===========================

1) STANDALONE APPLICATIONS

2) APPLETS

STANDALONE APPLICATIONS :- THESE ARE GENERAL PROGRAMS WHICH ARE NOT RELATED TO INTERNET. THESE APPLICATIONS ARE EXECUTED BY JAVA INTERPRETER. THESE APPLICATIONS CONTAINS MAIN( ) METHOD. SO PROGRAM EXECUTION STARTS FROM MAIN( ) METHOD ONLY.

APPLETS :- THESE ARE SMALL WEB PROGRAMS. APPLETS ARE EXECUTED BY WEB BROWSER (GOOGLE, MOZILLA FIREFOX) OR APPLET VIEWER TOOL. BECAUSE THESE APPLICATIONS DON'T HAVE MAIN( ) METHOD.

Example:

class First
{
public static void main(String args[ ])
{
System.out.print("Welcome to Java Programming");
}
}

OUTPUT
========
Welcome to Java Programming 

Abstract method in java with example

ABSTRACT METHOD

AN ABSTRACT METHOD IS A METHOD, WHICH HAVE NO BODY. THE SUB CLASS MUST OVERRIDE ABSTRACT METHOD. IF A CLASS CONTAINS AT LEAST ONE ABSTRACT METHOD, THEN THAT CLASS MUST BE DECLARED AS AN ABSTRACT CLASS. WE CAN'T CREATE OBJECT FROM THE ABSTRACT CLASS DIRECTLY. BUT WE CAN CREATE REFERENCE FROM THE ABSTRACT CLASS.

AN EXAMPLE OF ABSTRACT CLASS:

abstract class Zero
{
abstract void show( );
};
class One extends Zero
{
void show( )
{
System.out.println("Display Method From Class One");
}
};
class AbsModel
{
public static void main(String args[])
{
One ob = new One( );
ob.show( );
}
}

IN ABSTRACT CLASS WE CAN ALSO HAS A CONCRETE METHODS:

abstract class Zero
{
abstract void show( );
void display( )
{
System.out.println("Display Method Called From Class One");
}
};
class One extends Zero
{
void show( )
{
System.out.println("Display Method From Class One");
}
};
class AbsModel
{
public static void main(String args[])
{
One ob = new One( );
ob.show( );
ob.display();
}
}

RESULTS:

Display Method From Class One
Display Method Called From Class One
                                       

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