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
                                       

                                         COMMENT YOUR IDEAS ABOUT TOPIC

why we use capacitor in ceiling fan

                                        USE OF CAPACITOR IN A CEILING FAN

Fan mostly operates with a single phase induction motor. As it is not a self starting motor, it needs a rotating magnetic field to start. to two make it a self starting motor a condenser ( usually known as capacitor) is connected to it to give a starting push up , instead of external winding known as auxiliary winding. Single phase supply on stator of this motor  gives alternating magnetic field but we need rotating magnetic field, so we use condensers.  capacitors

are used to split the phase and make it operate like a multi phase motor , so that rotating magnetic field is developed and the motor becomes self starting.

So  capacitor start capacitor run motors are used mostly in ceiling  fans.

Example of reading data through Scanner Class

         USING SCANNER CLASS TO INPUT 

BY USING THIS CLASS WE CAN DIRECTLY CONNECT WITH KEYBOARD. THE MAIN ADVANTAGE OF USING THIS CLASS IS TO READ NUMERIC TYPES OF DATA WITHOUT CONVERTING IT. IT IS AVAILABLE IN java.util PACKAGE. THIS CLASS HAS THE FOLLOWING METHODS :

next( ), nextLine( ), nextByte( ), nextShort( ), nextInt( ),nextFloat( ), nextDouble( ) etc.



Example of using Scanner to a normal results of student program:

   

import java.io.PrintStream;
import java.util.Scanner;
class Program                                         // Program is a Class word and 'P' should be in capital form
{
public static void main(String args[])
{
PrintStream ps = new PrintStream(System.out);
Scanner sc = new Scanner(System.in);
int sno,em,tm,hm,mm,scm,som,tot;
float avg;
String sname,res;
ps.println("Enter Student Number and Name");
sno = sc.nextInt( );
sname = sc.next( );
ps.println("Enter English, Telugu and Hindi Marks");
em = sc.nextInt( );
tm = sc.nextInt( );
hm = sc.nextInt( );
ps.println("Enter Maths, Science and Social Marks");
mm = sc.nextInt( );
scm = sc.nextInt( );
som = sc.nextInt( );
tot = em + tm + hm + mm + scm + som;
avg = tot / 6.0F;
if(em >= 34 && tm >= 34 && hm >= 34 && mm >= 34 && scm >= 34 && som >= 34 && avg >= 80)
{
res = "Distinction";
}
else
if(em >= 34 && tm >= 34 && hm >= 34 && mm >= 34 && scm >= 34 && som >= 34 && avg >= 60)
{
res = "First Class";
}
else
if(em >= 34 && tm >= 34 && hm >= 34 && mm >= 34 && scm >= 34 && som >= 34 && avg >= 50)
{
res = "Second Class";
}
else
if(em >= 34 && tm >= 34 && hm >= 34 && mm >= 34 && scm >= 34 && som >= 34 && avg >= 40)
{
res = "Third Class";
}
else
if(em >= 34 && tm >= 34 && hm >= 34 && mm >= 34 && scm >= 34 && som >= 34 && avg >= 34)
{
res = "Ordinary Pass";
}
else
{
res = "Fail";
}
ps.println("\t\t Abc School");
ps.println("\t\t=================");
ps.println("Student Number : " + sno);
ps.println("Student Name : " + sname);
ps.println("Total Marks : " + tot);
ps.printf("Average Marks : %.3f\n",avg);
ps.print("Result : " + res);
}
}


RESULT:

Enter Student Number and Name
2
JOHN
Enter English, Telugu and Hindi Marks
60
70
87

Enter Maths, Science and Social Marks
90
87
75
Abc School
        =================
Student Number : 2
Student Name : JOHN
Total Marks : 469
Average Marks : 78.167
Result : First Class

Inheritance topic

INHERITANCE IN JAVA

INHERITANCE IS THE TECHNIQUE OF EXTENSION OF ALREADY EXISTING CLASS. IT MEANS WE CAN PRODUCE NEW CLASS FROM EXISTING CLASS . IN THIS PROCESS, EXISTING CLASS IS CALLED AS SUPER CLASS / BASE CLASS  AND THE EXTENDED CLASS IS CALLED AS SUB CLASS / DERIVED CLASS / NEW CLASS. SUB CLASS IS 

POWERFUL THAN SUPER CLASS, BECAUSE SUB CLASS HAVE ALL THE FEATURES OF SUPER CLASS AND ADDITIONAL FEATURES OF ITSELF. THE MAIN ADVANTAGE OF INHERITANCE IS REUSABILITY OF CODE. IF WE CREATE AN OBJECT TO SUB CLASS IT CONTAINS A COPY OF SUPER CLASS OBJECT. THAT IS THE REASON WHY SUPER CLASS MEMBERS ARE AVAILABLE TO SUB CLASS. GENERALLY WE DON'T CREATE AN OBJECT TO SUPER CLASS IN INHERITANCE. SO BETTER WAY IS CREATE OBJECT TO SUB CLASS NOT TO SUPER CLASS.

           TYPES OF INHERITANCE

           ======================

            1) SINGLE INHERITANCE

            2) MULTI LEVEL INHERITANCE

            3) HIERARCHICAL INHERITANCE

            4) MULTIPLE INHERITANCE

            5) HYBRID INHERITANCE

JAVA'S RULE IS THAT A CLASS CAN HAVE ONLY ONE SUPER CLASS. SO JAVA DOES NOT SUPPORT MULTIPLE, MULTI PATH AND HYBRID INHERITANCES DIRECTLY.

1)    SINGLE INHERITANCE
   
       DERIVING NEW CLASS FROM SINGLE CLASS.
2)    MULTILEVEL INHERITANCE
     
       DERIVING NEW CLASS FROM ANOTHER DERIVED CLASS.
3)   HIERARCHICAL INHERITANCE

      THIS TYPE OF INHERITANCE IS SIMILAR TO A TREE. IN THIS MODEL EACH SUPER         CLASS HAS MINIMUM TWO SUB CLASSES. GENERALLY IN THIS MODEL OBJECTS           ARE CREATED FROM LEAF NODE (LAST SUB) CLASSES.

          MULTIPLE INHERITANCE  & HYBRID ARE NOT PREFERED.