1. Develop Rational number class in Java. Use JavaDoc comments for documentation. Your implementation should use efficient representation for a rational number, i.e. (500 / 1000) should be represented as (½).

import java.util.Scanner;public class Rational { /** * The Numerator part of Rational */

private int numerator; /** * The Denominator part of Rational */

private int denominator; /** * create and initialize a new Rational object */ public Rational(int numerator, int denominator) { if (denominator == 0) { throw new RuntimeException("Denominator is zero"); } int g = gcd(numerator, denominator); if (g == 1) { System.out.println("No Common Divisor for Numerator and Denominator"); this.numerator = numerator; this.denominator = denominator; } else { this.numerator = numerator / g; this.denominator = denominator / g; }

}

/** * return string representation of (this) */ public String toString() { return numerator + "/" + denominator; }

/** *

* @param m * @param n * @return Greatest common divisor for m and n */ private static int gcd(int m, int n) { if (0 == n) return m; else return gcd(n, m % n); }

/************************************************************************* * Test client *************************************************************************/

public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.print("Enter Numerator : "); int numerator = scanner.nextInt(); System.out.print("Enter Denominator : "); int denominator = scanner.nextInt(); Rational rational; rational = new Rational(numerator, denominator); System.out.println("Efficient Representation for the rational number :" + rational);

}

}

2. Develop Date class in Java similar to the one available in java.util package. Use JavaDoc comments.

import java.util.*;

public class Datedemo

{ public static void main(String args[])

{

/* Create date object with current date and time. */

Date date = new Date(); System.out.println("Today is " + date); } }

3. Implement Lisp-like list in Java. Write basic operations such as 'car', 'cdr', and 'cons'. If L is a list [3, 0, 2, 5], L.car() returns 3, while L.cdr() returns [0,2,5].

import java.util.ArrayList;import java.util.Arrays;import java.util.Collections;import java.util.List;import java.util.StringTokenizer;

import java.util.logging.Logger;

public class LispCommands {private String[] tokenList;

private static Logger LOGGER = Logger.getLogger(LispCommands.class.getName());

public LispCommands() {

}

private void car() {LOGGER.info(tokenList[0]);

}

private void cdr() {List<String> list = Arrays.asList(tokenList);ArrayList<String> slist = new ArrayList<String>(list);slist.remove(0);display(slist);

}

private void cons(String args) {List<String> arrayList = new

ArrayList<String>(Arrays.asList(tokenList));arrayList.add(args);Collections.reverse(arrayList);display(arrayList);

}

private void parse(String args) {ArrayList<String> tokenList = new ArrayList<String>();if(args != null){

StringTokenizer tokens = new StringTokenizer(args,"[]");

while (tokens.hasMoreElements()) {

StringTokenizer commaTokens = new StringTokenizer(tokens.nextToken(),",");

while (commaTokens.hasMoreElements()) {String token = commaTokens.nextToken();if(token != null && !token.trim().equals("")){

tokenList.add(token.trim());}

}

}}this.tokenList = tokenList.toArray(new String[0]);

}

private void display(Object result) {System.out.println();if(result instanceof String){

LOGGER.info(result.toString());} else if(result.getClass().getName().equals("java.util.ArrayList")){

LOGGER.info(result.toString());}}

public static void main(String[] args) {LispCommands L = new LispCommands();L.parse("[3, 0, 2, 5]");L.car();L.cdr();L.cons("7");

}}

5. Design a Vehicle class hierarchy in Java. Write a test program to demonstrate polymorphism.

import java.io.*;class Vehicle{String regno;int model;Vehicle(String r, int m){regno=r;model=m;}void display(){System.out.println("registration no:"+regno);System.out.println("model no:"+model); }}

class Twowheeler extends Vehicle{int noofwheel;Twowheeler(String r,int m,int n){super(r,m);noofwheel=n;}void display(){System.out.println("Two wheeler tvs");super.display();System.out.println("no of wheel" +noofwheel);}}

class Threewheeler extends Vehicle{int noofleaf;Threewheeler(String r,int m,int n){super(r,m);noofleaf=n;}void display(){

System.out.println("three wheeler auto");super.display();System.out.println("no of leaf" +noofleaf);}}

class Fourwheeler extends Vehicle{int noofleaf;Fourwheeler(String r,int m,int n){super(r,m);noofleaf=n;}void display(){System.out.println("four wheeler car");super.display();System.out.println("no of leaf" +noofleaf);}}

public class Vehicledemo{public static void main(String arg[]){Twowheeler t1;Threewheeler th1;Fourwheeler f1;t1=new Twowheeler("TN74 12345", 1,2);th1=new Threewheeler("TN74 54321", 4,3);f1=new Fourwheeler("TN34 45677",5,4);t1.display();th1.display();f1.display();}}

6. Design classes for Currency, Rupee, and Dollar. Write a program that randomly generates Rupee and Dollar objects and write them into a file using object serialization. Write another program to read that file, convert to Rupee if it reads a Dollar, while leave the value as it is if it reads a Rupee.

import java.io.Serializable;

public abstract class Currency implements Serializable {

protected static final Double DOLLAR_RUPEE_EXCHAGERATE = 44.445D;

public Currency(Double money) {super();this.money = money;

}

protected Double money;

public abstract Double getValue ();

public abstract String getPrintableValue();

}

/** * * @author Jana * */public class Rupee extends Currency {

public Rupee(Double amount) {super(amount);

}

@Overridepublic Double getValue() {

return this.money;}

@Overridepublic String getPrintableValue() {

String strValue = "Object Name : Rupee \nINR : Rs " + getValue() + "\n------------------\n";

return strValue;

}

}

public class Dollar extends Currency {

public Dollar(Double money) {super(money);

}

@Overridepublic Double getValue() {

return (this.money * DOLLAR_RUPEE_EXCHAGERATE);}

@Overridepublic String getPrintableValue() {

String strValue = "Object Name : Dollar \nUSD : $" + this.money + " \nINR : Rs" + getValue() + "\n------------------\n";

return strValue;}

}

import java.io.File;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectOutputStream;import java.util.Random;

public class StoreCurrency {

/** * * @param args * @throws FileNotFoundException * @throws IOException */public static void main(String[] args) throws FileNotFoundException,

IOException {

Currency currency = null;ObjectOutputStream out = new ObjectOutputStream(new

FileOutputStream(new File("currency.dat")));Random random = new Random();

for (int i = 0; i < 10; i++) {// Random generation of dollar or Rupee Objects int decide = random.nextInt();

// Random Generation of Dollar or Rupee valuesDouble value = (random.nextDouble() *10);

if ( (decide%2)==0 ) {currency = new Rupee(value);

} else {currency = new Dollar(value);

}out.writeObject(currency);

}out.writeObject(null); // To detect the end of the fileout.close();

}}import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.ObjectInputStream;

public class ReadCurrency {/**

* @param args * @throws ClassNotFoundException * @throws IOException * @throws IOException */public static void main(String[] args) throws IOException,

ClassNotFoundException {

Currency currency = null;ObjectInputStream in = new ObjectInputStream(new FileInputStream(new

File("currency.dat")));while ((currency = (Currency) in.readObject()) != null) {

System.out.println(currency.getPrintableValue());}in.close();

}

7. Design a scientific calculator using event-driven programming paradigm of Java.

import java.awt.*;import java.awt.event.*; // class CalcFrame for creating a calcul // ator frame and added windolistener to // close the calculator

class CalcFrame extends Frame {

CalcFrame( String str) { // call to superclass super(str); // to close the calculator(Frame)

addWindowListener(new WindowAdapter() {

public void windowClosing (WindowEvent we) { System.exit(0); }

});

}

}

// main class Calculator implemnets two // interfaces ActionListener // and ItemListener

public class Calculator implements ActionListener, ItemListener { // creating instances of objects CalcFrame fr; MenuBar mb; Menu view, font, about; MenuItem bold, regular, author; CheckboxMenuItem basic, scientific; CheckboxGroup cbg;

Checkbox radians, degrees; TextField display; Button key[] = new Button[20]; // creates a button object array of 20 Button clearAll, clearEntry, round;Button scientificKey[] = new Button[10]; // creates a button array of 8 // declaring variablesboolean addButtonPressed, subtractButtonPressed, multiplyButtonPressed;boolean divideButtonPressed, decimalPointPressed, powerButtonPressed;boolean roundButtonPressed = false;double initialNumber;// the first number for the two number operationdouble currentNumber = 0;//the number shown in the screen while it is //being pressedint decimalPlaces = 0; // main function

public static void main (String args[]) { // constructor Calculator calc = new Calculator(); calc.makeCalculator(); }

public void makeCalculator() { // size of the button final int BWIDTH = 25; final int BHEIGHT = 25; int count =1; // create frame for the calculator fr = new CalcFrame("Basic Calculator"); // set the size fr.setSize(200,270); fr.setBackground(Color.blue);; // create a menubar for the frame mb = new MenuBar(); // add menu the menubar view = new Menu("View"); font = new Menu ("Font"); about = new Menu("About"); // create instance of object for View me // nu basic = new CheckboxMenuItem("Basic",true); // add a listener to receive item events // when the state of an item changes basic.addItemListener(this); scientific = new CheckboxMenuItem("Scientific");

// add a listener to receive item events // when the state of an item changes scientific.addItemListener(this); // create instance of object for font me // nu bold = new MenuItem("Arial Bold"); bold.addActionListener(this); regular = new MenuItem("Arial Regular"); regular.addActionListener(this); // for about menu author = new MenuItem("Author"); author.addActionListener(this); // add the items in the menu view.add(basic); view.add(scientific); font.add(bold); font.add(regular); about.add(author); // add the menus in the menubar mb.add(view); mb.add(font); mb.add(about); // add menubar to the frame fr.setMenuBar(mb); // override the layout manager fr.setLayout(null); // set the initial numbers that is 1 to // 9

for (int row = 0; row < 3; ++row) {

for (int col = 0; col < 3; ++col) { // this will set the key from 1 to 9 key[count] = new Button(Integer.toString(count)); key[count].addActionListener(this); // set the boundry for the keys key[count].setBounds(30*(col + 1), 30*(row + 4),BWIDTH,BHEIGHT); key[count].setBackground(Color.yellow); // add to the frame fr.add(key[count++]); }

}

// Now create, addlistener and add to fr // ame all other keys //0 key[0] = new Button("0"); key[0].addActionListener(this); key[0].setBounds(30,210,BWIDTH,BHEIGHT); key[0].setBackground(Color.yellow); fr.add(key[0]); //decimal key[10] = new Button("."); key[10].addActionListener(this); key[10].setBounds(60,210,BWIDTH,BHEIGHT); key[10].setBackground(Color.yellow); fr.add(key[10]); //equals to key[11] = new Button("="); key[11].addActionListener(this); key[11].setBounds(90,210,BWIDTH,BHEIGHT); key[11].setBackground(Color.yellow); fr.add(key[11]); //multiply key[12] = new Button("*"); key[12].addActionListener(this); key[12].setBounds(120,120,BWIDTH,BHEIGHT); key[12].setBackground(Color.yellow); fr.add(key[12]); //divide key[13] = new Button("/"); key[13].addActionListener(this); key[13].setBounds(120,150,BWIDTH,BHEIGHT); key[13].setBackground(Color.yellow); fr.add(key[13]); //addition key[14] = new Button("+"); key[14].addActionListener(this); key[14].setBounds(120,180,BWIDTH,BHEIGHT); key[14].setBackground(Color.yellow); fr.add(key[14]); //subtract key[15] = new Button("-"); key[15].addActionListener(this); key[15].setBounds(120,210,BWIDTH,BHEIGHT); key[15].setBackground(Color.yellow); fr.add(key[15]); //reciprocal key[16] = new Button("1/x");

key[16].addActionListener(this); key[16].setBounds(150,120,BWIDTH,BHEIGHT); key[16].setBackground(Color.yellow); fr.add(key[16]); //power key[17] = new Button("x^n"); key[17].addActionListener(this); key[17].setBounds(150,150,BWIDTH,BHEIGHT); key[17].setBackground(Color.yellow); fr.add(key[17]); //change sign key[18] = new Button("+/-"); key[18].addActionListener(this); key[18].setBounds(150,180,BWIDTH,BHEIGHT); key[18].setBackground(Color.yellow); fr.add(key[18]); //factorial key[19] = new Button("x!"); key[19].addActionListener(this); key[19].setBounds(150,210,BWIDTH,BHEIGHT); key[19].setBackground(Color.yellow); fr.add(key[19]); // CA clearAll = new Button("CA"); clearAll.addActionListener(this); clearAll.setBounds(30, 240, BWIDTH+20, BHEIGHT); clearAll.setBackground(Color.yellow); fr.add(clearAll); // CE clearEntry = new Button("CE"); clearEntry.addActionListener(this); clearEntry.setBounds(80, 240, BWIDTH+20, BHEIGHT); clearEntry.setBackground(Color.yellow); fr.add(clearEntry); // round round = new Button("Round"); round.addActionListener(this); round.setBounds(130, 240, BWIDTH+20, BHEIGHT); round.setBackground(Color.yellow); fr.add(round); // set display area display = new TextField("0"); display.setBounds(30,90,150,20); display.setBackground(Color.white); // key for scientific calculator // Sine

scientificKey[0] = new Button("Sin"); scientificKey[0].addActionListener(this); scientificKey[0].setBounds(180, 120, BWIDTH + 10, BHEIGHT); scientificKey[0].setVisible(false); scientificKey[0].setBackground(Color.yellow); fr.add(scientificKey[0]); // cosine scientificKey[1] = new Button("Cos"); scientificKey[1].addActionListener(this); scientificKey[1].setBounds(180, 150, BWIDTH + 10, BHEIGHT); scientificKey[1].setBackground(Color.yellow); scientificKey[1].setVisible(false); fr.add(scientificKey[1]); // Tan scientificKey[2] = new Button("Tan"); scientificKey[2].addActionListener(this); scientificKey[2].setBounds(180, 180, BWIDTH + 10, BHEIGHT); scientificKey[2].setBackground(Color.yellow); scientificKey[2].setVisible(false); fr.add(scientificKey[2]); // PI scientificKey[3] = new Button("Pi"); scientificKey[3].addActionListener(this); scientificKey[3].setBounds(180, 210, BWIDTH + 10, BHEIGHT); scientificKey[3].setBackground(Color.yellow); scientificKey[3].setVisible(false); fr.add(scientificKey[3]); // aSine scientificKey[4] = new Button("aSin"); scientificKey[4].addActionListener(this); scientificKey[4].setBounds(220, 120, BWIDTH + 10, BHEIGHT); scientificKey[4].setBackground(Color.yellow); scientificKey[4].setVisible(false); fr.add(scientificKey[4]); // aCos scientificKey[5] = new Button("aCos"); scientificKey[5].addActionListener(this); scientificKey[5].setBounds(220, 150, BWIDTH + 10, BHEIGHT); scientificKey[5].setBackground(Color.yellow); scientificKey[5].setVisible(false); fr.add(scientificKey[5]); // aTan scientificKey[6] = new Button("aTan"); scientificKey[6].addActionListener(this); scientificKey[6].setBounds(220, 180, BWIDTH + 10, BHEIGHT); scientificKey[6].setBackground(Color.yellow);

scientificKey[6].setVisible(false); fr.add(scientificKey[6]); // E scientificKey[7] = new Button("E"); scientificKey[7].addActionListener(this); scientificKey[7].setBounds(220, 210, BWIDTH + 10, BHEIGHT); scientificKey[7].setBackground(Color.yellow); scientificKey[7].setVisible(false); fr.add(scientificKey[7]); // to degrees scientificKey[8] = new Button("todeg"); scientificKey[8].addActionListener(this); scientificKey[8].setBounds(180, 240, BWIDTH + 10, BHEIGHT); scientificKey[8].setBackground(Color.yellow); scientificKey[8].setVisible(false); fr.add(scientificKey[8]); // to radians scientificKey[9] = new Button("torad"); scientificKey[9].addActionListener(this); scientificKey[9].setBounds(220, 240, BWIDTH + 10, BHEIGHT); scientificKey[9].setBackground(Color.yellow); scientificKey[9].setVisible(false); fr.add(scientificKey[9]); cbg = new CheckboxGroup(); degrees = new Checkbox("Degrees", cbg, true); radians = new Checkbox("Radians", cbg, false); degrees.addItemListener(this); radians.addItemListener(this); degrees.setBounds(185, 75, 3 * BWIDTH, BHEIGHT); radians.setBounds(185, 95, 3 * BWIDTH, BHEIGHT); degrees.setVisible(false); radians.setVisible(false); fr.add(degrees); fr.add(radians); fr.add(display); fr.setVisible(true); } // end of makeCalculator

public void actionPerformed(ActionEvent ae) { String buttonText = ae.getActionCommand(); double displayNumber = Double.valueOf(display.getText()).doubleValue(); // if the button pressed text is 0 to 9

if((buttonText.charAt(0) >= '0') & (buttonText.charAt(0) <= '9')) {

if(decimalPointPressed) { for (int i=1;i <=decimalPlaces; ++i) currentNumber *= 10; currentNumber +=(int)buttonText.charAt(0)- (int)'0';

for (int i=1;i <=decimalPlaces; ++i) { currentNumber /=10; }

++decimalPlaces; display.setText(Double.toString(currentNumber)); }

else if (roundButtonPressed) { int decPlaces = (int)buttonText.charAt(0) - (int)'0'; for (int i=0; i< decPlaces; ++i) displayNumber *=10; displayNumber = Math.round(displayNumber);

for (int i = 0; i < decPlaces; ++i) { displayNumber /=10; }

display.setText(Double.toString(displayNumber)); roundButtonPressed = false; }

else { currentNumber = currentNumber * 10 + (int)buttonText.charAt(0)-(int)'0'; display.setText(Integer.toString((int)currentNumber)); }

}

// if button pressed is addition

if(buttonText == "+") { addButtonPressed = true; initialNumber = displayNumber; currentNumber = 0; decimalPointPressed = false; }

// if button pressed is subtract

if (buttonText == "-") { subtractButtonPressed = true; initialNumber = displayNumber; currentNumber = 0; decimalPointPressed = false; }

// if button pressed is divide

if (buttonText == "/") { divideButtonPressed = true; initialNumber = displayNumber; currentNumber = 0; decimalPointPressed = false; }

// if button pressed is multiply

if (buttonText == "*") { multiplyButtonPressed = true; initialNumber = displayNumber; currentNumber = 0; decimalPointPressed = false; }

// if button pressed is reciprocal

if (buttonText == "1/x") { // call reciprocal method display.setText(reciprocal(displayNumber)); currentNumber = 0; decimalPointPressed = false; }

// if button is pressed to change a sign //

if (buttonText == "+/-") { // call changesign meyhod to change the // sign display.setText(changeSign(displayNumber)); currentNumber = 0; decimalPointPressed = false; }

// factorial button

if (buttonText == "x!") { display.setText(factorial(displayNumber)); currentNumber = 0; decimalPointPressed = false; }

// power button

if (buttonText == "x^n") { powerButtonPressed = true; initialNumber = displayNumber; currentNumber = 0; decimalPointPressed = false; }

// now for scientific buttons

if (buttonText == "Sin") { if (degrees.getState()) display.setText(Double.toString(Math.sin(Math.PI * displayNumber/180)));

else { display.setText(Double.toString(Math.sin(displayNumber))); currentNumber = 0; decimalPointPressed = false; }

}

if (buttonText == "Cos") { if (degrees.getState()) display.setText(Double.toString(Math.cos(Math.PI * displayNumber/180)));

else{ display.setText(Double.toString(Math.cos(displayNumber))); currentNumber = 0; decimalPointPressed = false; }

}

if (buttonText == "Tan") { if (degrees.getState()) display.setText(Double.toString(Math.tan(Math.PI * displayNumber/180)));

else { display.setText(Double.toString(Math.tan(displayNumber))); currentNumber = 0; decimalPointPressed = false; }

}

if (buttonText == "aSin") { if (degrees.getState()) display.setText(Double.toString(Math.asin(displayNumber)* 180/Math.PI ));

else { display.setText(Double.toString(Math.asin(displayNumber))); currentNumber = 0; decimalPointPressed = false; }

}

if (buttonText == "aCos") { if (degrees.getState()) display.setText(Double.toString(Math.acos(displayNumber)* 180/Math.PI ));

else { display.setText(Double.toString(Math.acos(displayNumber))); currentNumber = 0; decimalPointPressed = false; }

}

if (buttonText == "aTan") { if (degrees.getState()) display.setText(Double.toString(Math.atan(displayNumber)* 180/Math.PI ));

else { display.setText(Double.toString(Math.atan(displayNumber))); currentNumber = 0; decimalPointPressed = false; }

}

// this will convert the numbers display // ed to degrees if (buttonText == "todeg") display.setText(Double.toString(Math.toDegrees(displayNumber))); // this will convert the numbers display // ed to radians if (buttonText == "torad") display.setText(Double.toString(Math.toRadians(displayNumber)));

if (buttonText == "Pi") { display.setText(Double.toString(Math.PI)); currentNumber =0; decimalPointPressed = false; }

if (buttonText == "Round") roundButtonPressed = true; // check if decimal point is pressed

if (buttonText == ".") { String displayedNumber = display.getText(); boolean decimalPointFound = false; int i; decimalPointPressed = true; // check for decimal point

for (i =0; i < displayedNumber.length(); ++i) {

if(displayedNumber.charAt(i) == '.') { decimalPointFound = true; continue; }

}

if (!decimalPointFound) decimalPlaces = 1; }

if(buttonText == "CA"){ // set all buttons to false resetAllButtons(); display.setText("0"); currentNumber = 0; }

if (buttonText == "CE") { display.setText("0"); currentNumber = 0; decimalPointPressed = false; }

if (buttonText == "E") { display.setText(Double.toString(Math.E)); currentNumber = 0; decimalPointPressed = false; }

// the main action

if (buttonText == "=") { currentNumber = 0; // if add button is pressed if(addButtonPressed) display.setText(Double.toString(initialNumber + displayNumber)); // if subtract button is pressed if(subtractButtonPressed) display.setText(Double.toString(initialNumber - displayNumber)); // if divide button is pressed

if (divideButtonPressed) { // check if the divisor is zero

if(displayNumber == 0) { MessageBox mb = new MessageBox ( fr, "Error ", true, "Cannot divide by zero."); mb.show(); }

else display.setText(Double.toString(initialNumber/displayNumber)); }

// if multiply button is pressed if(multiplyButtonPressed) display.setText(Double.toString(initialNumber * displayNumber)); // if power button is pressed if (powerButtonPressed) display.setText(power(initialNumber, displayNumber)); // set all the buttons to false resetAllButtons(); }

if (buttonText == "Arial Regular") { for (int i =0; i < 10; ++i) key[i].setFont(new Font("Arial", Font.PLAIN, 12)); }

if (buttonText == "Arial Bold") { for (int i =0; i < 10; ++i) key[i].setFont(new Font("Arial", Font.BOLD, 12)); }

if (buttonText == "Author") {MessageBox mb = new MessageBox ( fr, "Calculator ver 1.0 beta ", true, "Author: Inder Mohan Singh."); mb.show(); }

} // end of action events

public void itemStateChanged(ItemEvent ie) {

if (ie.getItem() == "Basic") { basic.setState(true); scientific.setState(false); fr.setTitle("Basic Calculator"); fr.setSize(200,270); // check if the scientific keys are visi // ble. if true hide them

if (scientificKey[0].isVisible()) { for (int i=0; i < 8; ++i) scientificKey[i].setVisible(false); radians.setVisible(false); degrees.setVisible(false); }

}

if (ie.getItem() == "Scientific") { basic.setState(false); scientific.setState(true); fr.setTitle("Scientific Calculator"); fr.setSize(270,270); // check if the scientific keys are visi // ble. if true display them

if (!scientificKey[0].isVisible()) { for (int i=0; i < 10; ++i) scientificKey[i].setVisible(true); radians.setVisible(true); degrees.setVisible(true); }

}

} // end of itemState

// this method will reset all the button // Pressed property to false

public void resetAllButtons() { addButtonPressed = false; subtractButtonPressed = false; multiplyButtonPressed = false; divideButtonPressed = false; decimalPointPressed = false; powerButtonPressed = false; roundButtonPressed = false; }

public String factorial(double num) { int theNum = (int)num;

if (theNum < 1) { MessageBox mb = new MessageBox (fr, "Facorial Error", true, "Cannot find the factorial of numbers less than 1."); mb.show();

return ("0"); }

else { for (int i=(theNum -1); i > 1; --i) theNum *= i; return Integer.toString(theNum); }

}

public String reciprocal(double num) {

if (num ==0) { MessageBox mb = new MessageBox(fr,"Reciprocal Error", true, "Cannot find the reciprocal of 0"); mb.show(); }

else num = 1/num; return Double.toString(num); }

public String power (double base, double index) { return Double.toString(Math.pow(base, index)); }

public String changeSign(double num) { return Double.toString(-num); }

}

class MessageBox extends Dialog implements ActionListener {

Button ok;

MessageBox(Frame f, String title, boolean mode, String message) { super(f, title, mode); Panel centrePanel = new Panel(); Label lbl = new Label(message); centrePanel.add(lbl); add(centrePanel, "Center"); Panel southPanel = new Panel(); ok = new Button ("OK"); ok.addActionListener(this); southPanel.add(ok); add(southPanel, "South"); pack();

addWindowListener (new WindowAdapter() {

public void windowClosing (WindowEvent we) { System.exit(0); }

}); }

public void actionPerformed(ActionEvent ae) { dispose(); }

}

<applet code= "Calculator.class" width=200 Height=700></applet>

9. Develop a simple OPAC system for library using even-driven and concurrent programming paradigms of Java. Use JDBC to connect to a back-end database.

Event driven

import java.sql.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class Datas extends JFrame implements ActionListener {

JTextField id;JTextField name;JButton next;JButton addnew;JPanel p;static ResultSet res;static Connection conn;static Statement stat;

public Datas(){

super("Our Application");Container c = getContentPane();c.setLayout(new GridLayout(5,1));id = new JTextField(20);name = new JTextField(20);next = new JButton("Next BOOK");p = new JPanel();c.add(new JLabel("ISBN",JLabel.CENTER));c.add(id);

c.add(new JLabel("Book Name",JLabel.CENTER));c.add(name);c.add(p);p.add(next);

next.addActionListener(this); pack();

setVisible(true);addWindowListener(new WIN());

}

public static void main(String args[]) {Datas d = new Datas();try {Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

conn = DriverManager.getConnection("jdbc:odbc:custo"); // cust is the DSN Name

stat = conn.createStatement();res = stat.executeQuery("Select * from stu"); // Customers is the table name

res.next();

}catch(Exception e) {System.out.println("Error" +e);}d.showRecord(res);}

public void actionPerformed(ActionEvent e) {if(e.getSource() == next) {try {res.next();}catch(Exception ee) {}showRecord(res);}}

public void showRecord(ResultSet res) {try {id.setText(res.getString(2));name.setText(res.getString(3));}catch(Exception e) {}

}//end of the main //Inner class WIN implemented class WIN extends WindowAdapter { public void windowClosing(WindowEvent w) {

JOptionPane jop = new JOptionPane();

jop.showMessageDialog(null,"Database","Thanks",JOptionPane.QUESTION_MESSAGE);

} } } //end of the class

Concurrent

import java.sql.*;import java.sql.DriverManager.*;class Ja{

String bookid,bookname;int booksno;Connection con;Statement stmt;ResultSet rs;Ja(){

try{

Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");con=DriverManager.getConnection("jdbc:odbc:co");

}catch(Exception e){System.out.println("connection error");}

}

void myput(){

try{

stmt=con.createStatement();rs=stmt.executeQuery("SELECT * FROM opac");while(rs.next()){

booksno=rs.getInt(1);bookid=rs.getString(2);bookname=rs.getString(3);System.out.println("\n"+ booksno+"\t"+bookid+"\

t"+bookname);}rs.close();stmt.close();con.close();

}catch(SQLException e){

System.out.println("sql error");}

}}class prog1{

public static void main(String arg[]){Ja j=new Ja();j.myput();}}

10. Develop multi-threaded echo server and a corresponding GUI client in Java.

import java.net.*; import java.io.*;

public class EchoServer { ServerSocket m_ServerSocket; public EchoServer() { try { // Create the server socket. m_ServerSocket = new ServerSocket(12111); } catch(IOException ioe) { System.out.println("Could not create server socket at 12111. Quitting."); System.exit(-1); } System.out.println("Listening for clients....."); // Successfully created Server Socket. Now wait for connections. int id = 0; while(true) { try { // Accept incoming connections. Socket clientSocket = m_ServerSocket.accept(); // accept() will block until a client connects to the server. // If execution reaches this point, then it means that a client // socket has been accepted. // For each client, we will start a service thread to // service the client requests. This is to demonstrate a // multithreaded server, although not required for such a // trivial application. Starting a thread also lets our // EchoServer accept multiple connections simultaneously.

// Start a service thread ClientServiceThread cliThread = new ClientServiceThread(clientSocket, id++); cliThread.start(); } catch(IOException ioe) { System.out.println("Exception encountered on accept. Ignoring. Stack Trace :"); ioe.printStackTrace(); } } } public static void main (String[] args) { new EchoServer(); } class ClientServiceThread extends Thread { Socket m_clientSocket; int m_clientID = -1; boolean m_bRunThread = true; ClientServiceThread(Socket s, int clientID) { m_clientSocket = s; m_clientID = clientID; } public void run() { // Obtain the input stream and the output stream for the socket // A good practice is to encapsulate them with a BufferedReader // and a PrintWriter as shown below. BufferedReader in = null; PrintWriter out = null; // Print out details of this connection System.out.println("Accepted Client : ID - " + m_clientID + " : Address - " + m_clientSocket.getInetAddress().getHostName()); try {

in = new BufferedReader(new InputStreamReader(m_clientSocket.getInputStream())); out = new PrintWriter(new OutputStreamWriter(m_clientSocket.getOutputStream())); // At this point, we can read for input and reply with appropriate output. // Run in a loop until m_bRunThread is set to false while(m_bRunThread) { // read incoming stream String clientCommand = in.readLine(); System.out.println("Client Says :" + clientCommand); if(clientCommand.equalsIgnoreCase("quit")) { // Special command. Quit this thread m_bRunThread = false; System.out.print("Stopping client thread for client : " + m_clientID); } else { // Echo it back to the client. out.println(clientCommand); out.flush(); } } } catch(Exception e) { e.printStackTrace(); } finally { // Clean up try { in.close(); out.close(); m_clientSocket.close(); System.out.println("...Stopped"); } catch(IOException ioe) {

ioe.printStackTrace(); } } } } }

import java.net.*; import java.io.*;

// A client for our multithreaded EchoServer. public class EchoClient { public static void main(String[] args) { // First parameter has to be machine name if(args.length == 0) { System.out.println("Usage : EchoClient <serverName>"); return; } Socket s = null; // Create the socket connection to the EchoServer. try { s = new Socket(args[0], 12111); } catch(UnknownHostException uhe) { // Host unreachable System.out.println("Unknown Host :" + args[0]); s = null; } catch(IOException ioe) { // Cannot connect to port on given host System.out.println("Cant connect to server at 12111. Make sure it is running."); s = null; } if(s == null) System.exit(-1);

BufferedReader in = null; PrintWriter out = null; try { // Create the streams to send and receive information in = new BufferedReader(new InputStreamReader(s.getInputStream())); out = new PrintWriter(new OutputStreamWriter(s.getOutputStream())); // Since this is the client, we will initiate the talking. // Send a string. out.println("Hello"); out.flush(); // receive the reply. System.out.println("Server Says : " + in.readLine()); // Send a string. out.println("This"); out.flush(); // receive a reply. System.out.println("Server Says : " + in.readLine()); // Send a string. out.println("is"); out.flush(); // receive a reply. System.out.println("Server Says : " + in.readLine()); // Send a string. out.println("a"); out.flush(); // receive a reply. System.out.println("Server Says : " + in.readLine());

// Send a string. out.println("Test"); out.flush(); // receive a reply. System.out.println("Server Says : " + in.readLine()); // Send the special string to tell server to quit. out.println("Quit"); out.flush(); } catch(IOException ioe) {

System.out.println("Exception during communication. Server probably closed connection."); } finally { try { // Close the streams out.close(); in.close(); // Close the socket before quitting s.close(); } catch(Exception e) { e.printStackTrace(); } } } }