Question

create a Visual Basic project with the following features:

1. The user interface can display the following information, one textbox for one item:

1a. Author, in the form of Lastname, Firstname

1b. Title

1c. Source -- where the paper is published

1d. Abstract 1e. Publication year (This information is in the 1c. Source, but display the publication year separately here)

2. There is a command button "Import". It would allow the user to select the eric.txt as the input file and save the random file on the disk. With this function, you need to define a data structure for the record in the random file. Do some study on the data in eric.txt and design your own data structure. Generally speaking, if you save the data into multiple fields, it is easy to put these fields together if you need them. In contrast, if your data has multiple components, it is hard to separate the data when you need to.

3. There is an "Open File" button. This will open the random access file created in step 2. Whenever the file needs to be accessed, the user should not have to open a file anymore unless the user wants to change a file. When the file is open, the Import button should be disabled. After the file is opened, the first record should be displayed on the screen.

4. There is a Next button and a Previous button. When the first record is being displayed, the Previous button should be disabled. When the last record is displayed, the next button should be disabled.

Answer 1

1

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.sql.*;

import java.text.DateFormat;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.ArrayList;

import java.util.Date;

import java.util.Locale;

import java.util.concurrent.TimeUnit;

import javax.swing.*;

import net.proteanit.sql.DbUtils;

public class main {

public static class ex{

public static int days=0;

}

public static void main(String[] args) {

login();

//create();

}

public static void login() {

JFrame f=new JFrame("Login");//creating instance of JFrame

JLabel l1,l2;

l1=new JLabel("Username"); //Create label Username

l1.setBounds(30,15, 100,30); //x axis, y axis, width, height

l2=new JLabel("Password"); //Create label Password

l2.setBounds(30,50, 100,30);

JTextField F_user = new JTextField(); //Create text field for username

F_user.setBounds(110, 15, 200, 30);

JPasswordField F_pass=new JPasswordField(); //Create text field for password

F_pass.setBounds(110, 50, 200, 30);

JButton login_but=new JButton("Login");//creating instance of JButton for Login Button

login_but.setBounds(130,90,80,25);//Dimensions for button

login_but.addActionListener(new ActionListener() { //Perform action

public void actionPerformed(ActionEvent e){

String username = F_user.getText(); //Store username entered by the user in the variable "username"

String password = F_pass.getText(); //Store password entered by the user in the variable "password"

if(username.equals("")) //If username is null

{

JOptionPane.showMessageDialog(null,"Please enter username"); //Display dialog box with the message

}

else if(password.equals("")) //If password is null

{

JOptionPane.showMessageDialog(null,"Please enter password"); //Display dialog box with the message

}

else { //If both the fields are present then to login the user, check wether the user exists already

//System.out.println("Login connect");

Connection connection=connect(); //Connect to the database

try

{

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY"); //Use the database with the name "Library"

String st = ("SELECT * FROM USERS WHERE USERNAME='"+username+"' AND PASSWORD='"+password+"'"); //Retreive username and passwords from users

ResultSet rs = stmt.executeQuery(st); //Execute query

if(rs.next()==false) { //Move pointer below

System.out.print("No user");

JOptionPane.showMessageDialog(null,"Wrong Username/Password!"); //Display Message

}

else {

f.dispose();

rs.beforeFirst(); //Move the pointer above

while(rs.next())

{

String admin = rs.getString("ADMIN"); //user is admin

//System.out.println(admin);

String UID = rs.getString("UID"); //Get user ID of the user

if(admin.equals("1")) { //If boolean value 1

admin_menu(); //redirect to admin menu

}

else{

user_menu(UID); //redirect to user menu for that user ID

}

}

}

}

catch (Exception ex) {

ex.printStackTrace();

}

}

}

});

f.add(F_pass); //add password

f.add(login_but);//adding button in JFrame

f.add(F_user); //add user

f.add(l1); // add label1 i.e. for username

f.add(l2); // add label2 i.e. for password

f.setSize(400,180);//400 width and 500 height

f.setLayout(null);//using no layout managers

f.setVisible(true);//making the frame visible

f.setLocationRelativeTo(null);

}

//Connect

//The connect function is used to connect the database to the GUI. //So, to do that, I have mentioned the below code:

public static Connection connect()

{

try {

Class.forName("com.mysql.cj.jdbc.Driver");

//System.out.println("Loaded driver");

Connection con = DriverManager.getConnection("jdbc:mysql://localhost/mysql?user=root&password=edureka");

//System.out.println("Connected to MySQL");

return con;

}

catch (Exception ex) {

ex.printStackTrace();

}

return null;

}

public static void create() {

try {

Connection connection=connect();

ResultSet resultSet = connection.getMetaData().getCatalogs();

//iterate each catalog in the ResultSet

while (resultSet.next()) {

// Get the database name, which is at position 1

String databaseName = resultSet.getString(1);

if(databaseName.equals("library")) {

//System.out.print("yes");

Statement stmt = connection.createStatement();

//Drop database if it pre-exists to reset the complete database

String sql = "DROP DATABASE library";

stmt.executeUpdate(sql);

}

}

Statement stmt = connection.createStatement();

String sql = "CREATE DATABASE LIBRARY"; //Create Database

stmt.executeUpdate(sql);

stmt.executeUpdate("USE LIBRARY"); //Use Database

//Create Users Table

String sql1 = "CREATE TABLE USERS(UID INT NOT NULL AUTO_INCREMENT PRIMARY KEY, USERNAME VARCHAR(30), PASSWORD VARCHAR(30), ADMIN BOOLEAN)";

stmt.executeUpdate(sql1);

//Insert into users table

stmt.executeUpdate("INSERT INTO USERS(USERNAME, PASSWORD, ADMIN) VALUES('admin','admin',TRUE)");

//Create Books table

stmt.executeUpdate("CREATE TABLE BOOKS(BID INT NOT NULL AUTO_INCREMENT PRIMARY KEY, BNAME VARCHAR(50), GENRE VARCHAR(20), PRICE INT)");

//Create Issued Table

stmt.executeUpdate("CREATE TABLE ISSUED(IID INT NOT NULL AUTO_INCREMENT PRIMARY KEY, UID INT, BID INT, ISSUED_DATE VARCHAR(20), RETURN_DATE VARCHAR(20), PERIOD INT, FINE INT)");

//Insert into books table

stmt.executeUpdate("INSERT INTO BOOKS(BNAME, GENRE, PRICE) VALUES ('War and Peace', 'Mystery', 200), ('The Guest Book', 'Fiction', 300), ('The Perfect Murder','Mystery', 150), ('Accidental Presidents', 'Biography', 250), ('The Wicked King','Fiction', 350)");

resultSet.close();

}

catch (Exception ex) {

ex.printStackTrace();

}

}

public static void user_menu(String UID) {

JFrame f=new JFrame("User Functions"); //Give dialog box name as User functions

//f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Exit user menu on closing the dialog box

JButton view_but=new JButton("View Books");//creating instance of JButton

view_but.setBounds(20,20,120,25);//x axis, y axis, width, height

view_but.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

JFrame f = new JFrame("Books Available"); //View books stored in database

//f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

Connection connection = connect();

String sql="select * from BOOKS"; //Retreive data from database

try {

Statement stmt = connection.createStatement(); //connect to database

stmt.executeUpdate("USE LIBRARY"); // use librabry

stmt=connection.createStatement();

ResultSet rs=stmt.executeQuery(sql);

JTable book_list= new JTable(); //show data in table format

book_list.setModel(DbUtils.resultSetToTableModel(rs));

JScrollPane scrollPane = new JScrollPane(book_list); //enable scroll bar

f.add(scrollPane); //add scroll bar

f.setSize(800, 400); //set dimensions of view books frame

f.setVisible(true);

f.setLocationRelativeTo(null);

} catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

}

);

JButton my_book=new JButton("My Books");//creating instance of JButton

my_book.setBounds(150,20,120,25);//x axis, y axis, width, height

my_book.addActionListener(new ActionListener() { //Perform action

public void actionPerformed(ActionEvent e){

JFrame f = new JFrame("My Books"); //View books issued by user

//f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

int UID_int = Integer.parseInt(UID); //Pass user ID

//.iid,issued.uid,issued.bid,issued.issued_date,issued.return_date,issued,

Connection connection = connect(); //connect to database

//retrieve data

String sql="select distinct issued.*,books.bname,books.genre,books.price from issued,books " + "where ((issued.uid=" + UID_int + ") and (books.bid in (select bid from issued where issued.uid="+UID_int+"))) group by iid";

String sql1 = "select bid from issued where uid="+UID_int;

try {

Statement stmt = connection.createStatement();

//use database

stmt.executeUpdate("USE LIBRARY");

stmt=connection.createStatement();

//store in array

ArrayList books_list = new ArrayList();

ResultSet rs=stmt.executeQuery(sql);

JTable book_list= new JTable(); //store data in table format

book_list.setModel(DbUtils.resultSetToTableModel(rs));

//enable scroll bar

JScrollPane scrollPane = new JScrollPane(book_list);

f.add(scrollPane); //add scroll bar

f.setSize(800, 400); //set dimensions of my books frame

f.setVisible(true);

f.setLocationRelativeTo(null);

} catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

}

);

f.add(my_book); //add my books

f.add(view_but); // add view books

f.setSize(300,100);//400 width and 500 height

f.setLayout(null);//using no layout managers

f.setVisible(true);//making the frame visible

f.setLocationRelativeTo(null);

}

public static void admin_menu() {

JFrame f=new JFrame("Admin Functions"); //Give dialog box name as admin functions

//f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //

JButton create_but=new JButton("Create/Reset");//creating instance of JButton to create or reset database

create_but.setBounds(450,60,120,25);//x axis, y axis, width, height

create_but.addActionListener(new ActionListener() { //Perform action

public void actionPerformed(ActionEvent e){

create(); //Call create function

JOptionPane.showMessageDialog(null,"Database Created/Reset!"); //Open a dialog box and display the message

}

});

JButton view_but=new JButton("View Books");//creating instance of JButton to view books

view_but.setBounds(20,20,120,25);//x axis, y axis, width, height

view_but.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

JFrame f = new JFrame("Books Available");

//f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

Connection connection = connect(); //connect to database

String sql="select * from BOOKS"; //select all books

try {

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY"); //use database

stmt=connection.createStatement();

ResultSet rs=stmt.executeQuery(sql);

JTable book_list= new JTable(); //view data in table format

book_list.setModel(DbUtils.resultSetToTableModel(rs));

//mention scroll bar

JScrollPane scrollPane = new JScrollPane(book_list);

f.add(scrollPane); //add scrollpane

f.setSize(800, 400); //set size for frame

f.setVisible(true);

f.setLocationRelativeTo(null);

} catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

}

);

JButton users_but=new JButton("View Users");//creating instance of JButton to view users

users_but.setBounds(150,20,120,25);//x axis, y axis, width, height

users_but.addActionListener(new ActionListener() { //Perform action on click button

public void actionPerformed(ActionEvent e){

JFrame f = new JFrame("Users List");

//f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

Connection connection = connect();

String sql="select * from users"; //retrieve all users

try {

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY"); //use database

stmt=connection.createStatement();

ResultSet rs=stmt.executeQuery(sql);

JTable book_list= new JTable();

book_list.setModel(DbUtils.resultSetToTableModel(rs));

//mention scroll bar

JScrollPane scrollPane = new JScrollPane(book_list);

f.add(scrollPane); //add scrollpane

f.setSize(800, 400); //set size for frame

f.setVisible(true);

f.setLocationRelativeTo(null);

} catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

}

);

JButton issued_but=new JButton("View Issued Books");//creating instance of JButton to view the issued books

issued_but.setBounds(280,20,160,25);//x axis, y axis, width, height

issued_but.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

JFrame f = new JFrame("Users List");

//f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

Connection connection = connect();

String sql="select * from issued";

try {

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY");

stmt=connection.createStatement();

ResultSet rs=stmt.executeQuery(sql);

JTable book_list= new JTable();

book_list.setModel(DbUtils.resultSetToTableModel(rs));

JScrollPane scrollPane = new JScrollPane(book_list);

f.add(scrollPane);

f.setSize(800, 400);

f.setVisible(true);

f.setLocationRelativeTo(null);

} catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

}

);

JButton add_user=new JButton("Add User"); //creating instance of JButton to add users

add_user.setBounds(20,60,120,25); //set dimensions for button

add_user.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

JFrame g = new JFrame("Enter User Details"); //Frame to enter user details

//g.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//Create label

JLabel l1,l2;

l1=new JLabel("Username"); //label 1 for username

l1.setBounds(30,15, 100,30);

l2=new JLabel("Password"); //label 2 for password

l2.setBounds(30,50, 100,30);

//set text field for username

JTextField F_user = new JTextField();

F_user.setBounds(110, 15, 200, 30);

//set text field for password

JPasswordField F_pass=new JPasswordField();

F_pass.setBounds(110, 50, 200, 30);

//set radio button for admin

JRadioButton a1 = new JRadioButton("Admin");

a1.setBounds(55, 80, 200,30);

//set radio button for user

JRadioButton a2 = new JRadioButton("User");

a2.setBounds(130, 80, 200,30);

//add radio buttons

ButtonGroup bg=new ButtonGroup();

bg.add(a1);bg.add(a2);

JButton create_but=new JButton("Create");//creating instance of JButton for Create

create_but.setBounds(130,130,80,25);//x axis, y axis, width, height

create_but.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

String username = F_user.getText();

String password = F_pass.getText();

Boolean admin = false;

if(a1.isSelected()) {

admin=true;

}

Connection connection = connect();

try {

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY");

stmt.executeUpdate("INSERT INTO USERS(USERNAME,PASSWORD,ADMIN) VALUES ('"+username+"','"+password+"',"+admin+")");

JOptionPane.showMessageDialog(null,"User added!");

g.dispose();

}

catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

});

g.add(create_but);

g.add(a2);

g.add(a1);

g.add(l1);

g.add(l2);

g.add(F_user);

g.add(F_pass);

g.setSize(350,200);//400 width and 500 height

g.setLayout(null);//using no layout managers

g.setVisible(true);//making the frame visible

g.setLocationRelativeTo(null);

}

});

JButton add_book=new JButton("Add Book"); //creating instance of JButton for adding books

add_book.setBounds(150,60,120,25);

add_book.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

//set frame wot enter book details

JFrame g = new JFrame("Enter Book Details");

//g.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

// set labels

JLabel l1,l2,l3;

l1=new JLabel("Book Name"); //lebel 1 for book name

l1.setBounds(30,15, 100,30);

l2=new JLabel("Genre"); //label 2 for genre

l2.setBounds(30,53, 100,30);

l3=new JLabel("Price"); //label 2 for price

l3.setBounds(30,90, 100,30);

//set text field for book name

JTextField F_bname = new JTextField();

F_bname.setBounds(110, 15, 200, 30);

//set text field for genre

JTextField F_genre=new JTextField();

F_genre.setBounds(110, 53, 200, 30);

//set text field for price

JTextField F_price=new JTextField();

F_price.setBounds(110, 90, 200, 30);

JButton create_but=new JButton("Submit");//creating instance of JButton to submit details

create_but.setBounds(130,130,80,25);//x axis, y axis, width, height

create_but.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

// assign the book name, genre, price

String bname = F_bname.getText();

String genre = F_genre.getText();

String price = F_price.getText();

//convert price of integer to int

int price_int = Integer.parseInt(price);

Connection connection = connect();

try {

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY");

stmt.executeUpdate("INSERT INTO BOOKS(BNAME,GENRE,PRICE) VALUES ('"+bname+"','"+genre+"',"+price_int+")");

JOptionPane.showMessageDialog(null,"Book added!");

g.dispose();

}

catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

});

g.add(l3);

g.add(create_but);

g.add(l1);

g.add(l2);

g.add(F_bname);

g.add(F_genre);

g.add(F_price);

g.setSize(350,200);//400 width and 500 height

g.setLayout(null);//using no layout managers

g.setVisible(true);//making the frame visible

g.setLocationRelativeTo(null);

}

});

JButton issue_book=new JButton("Issue Book"); //creating instance of JButton to issue books

issue_book.setBounds(450,20,120,25);

issue_book.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

//enter details

JFrame g = new JFrame("Enter Details");

//g.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//create labels

JLabel l1,l2,l3,l4;

l1=new JLabel("Book ID(BID)"); // Label 1 for Book ID

l1.setBounds(30,15, 100,30);

l2=new JLabel("User ID(UID)"); //Label 2 for user ID

l2.setBounds(30,53, 100,30);

l3=new JLabel("Period(days)"); //Label 3 for period

l3.setBounds(30,90, 100,30);

l4=new JLabel("Issued Date(DD-MM-YYYY)"); //Label 4 for issue date

l4.setBounds(30,127, 150,30);

JTextField F_bid = new JTextField();

F_bid.setBounds(110, 15, 200, 30);

JTextField F_uid=new JTextField();

F_uid.setBounds(110, 53, 200, 30);

JTextField F_period=new JTextField();

F_period.setBounds(110, 90, 200, 30);

JTextField F_issue=new JTextField();

F_issue.setBounds(180, 130, 130, 30);

JButton create_but=new JButton("Submit");//creating instance of JButton

create_but.setBounds(130,170,80,25);//x axis, y axis, width, height

create_but.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

String uid = F_uid.getText();

String bid = F_bid.getText();

String period = F_period.getText();

String issued_date = F_issue.getText();

int period_int = Integer.parseInt(period);

Connection connection = connect();

try {

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY");

stmt.executeUpdate("INSERT INTO ISSUED(UID,BID,ISSUED_DATE,PERIOD) VALUES ('"+uid+"','"+bid+"','"+issued_date+"',"+period_int+")");

JOptionPane.showMessageDialog(null,"Book Issued!");

g.dispose();

}

catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

});

g.add(l3);

g.add(l4);

g.add(create_but);

g.add(l1);

g.add(l2);

g.add(F_uid);

g.add(F_bid);

g.add(F_period);

g.add(F_issue);

g.setSize(350,250);//400 width and 500 height

g.setLayout(null);//using no layout managers

g.setVisible(true);//making the frame visible

g.setLocationRelativeTo(null);

}

});

JButton return_book=new JButton("Return Book"); //creating instance of JButton to return books

return_book.setBounds(280,60,160,25);

return_book.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

JFrame g = new JFrame("Enter Details");

//g.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

//set labels

JLabel l1,l2,l3,l4;

l1=new JLabel("Issue ID(IID)"); //Label 1 for Issue ID

l1.setBounds(30,15, 100,30);

l4=new JLabel("Return Date(DD-MM-YYYY)");

l4.setBounds(30,50, 150,30);

JTextField F_iid = new JTextField();

F_iid.setBounds(110, 15, 200, 30);

JTextField F_return=new JTextField();

F_return.setBounds(180, 50, 130, 30);

JButton create_but=new JButton("Return");//creating instance of JButton to mention return date and calculcate fine

create_but.setBounds(130,170,80,25);//x axis, y axis, width, height

create_but.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent e){

String iid = F_iid.getText();

String return_date = F_return.getText();

Connection connection = connect();

try {

Statement stmt = connection.createStatement();

stmt.executeUpdate("USE LIBRARY");

//Intialize date1 with NULL value

String date1=null;

String date2=return_date; //Intialize date2 with return date

//select issue date

ResultSet rs = stmt.executeQuery("SELECT ISSUED_DATE FROM ISSUED WHERE IID="+iid);

while (rs.next()) {

date1 = rs.getString(1);

}

try {

Date date_1=new SimpleDateFormat("dd-MM-yyyy").parse(date1);

Date date_2=new SimpleDateFormat("dd-MM-yyyy").parse(date2);

//subtract the dates and store in diff

long diff = date_2.getTime() - date_1.getTime();

//Convert diff from milliseconds to days

ex.days=(int)(TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS));

} catch (ParseException e1) {

// TODO Auto-generated catch block

e1.printStackTrace();

}

//update return date

stmt.executeUpdate("UPDATE ISSUED SET RETURN_DATE='"+return_date+"' WHERE IID="+iid);

g.dispose();

Connection connection1 = connect();

Statement stmt1 = connection1.createStatement();

stmt1.executeUpdate("USE LIBRARY");

ResultSet rs1 = stmt1.executeQuery("SELECT PERIOD FROM ISSUED WHERE IID="+iid); //set period

String diff=null;

while (rs1.next()) {

diff = rs1.getString(1);

}

int diff_int = Integer.parseInt(diff);

if(ex.days>diff_int) { //If number of days are more than the period then calculcate fine

//System.out.println(ex.days);

int fine = (ex.days-diff_int)*10; //fine for every day after the period is Rs 10.

//update fine in the system

stmt1.executeUpdate("UPDATE ISSUED SET FINE="+fine+" WHERE IID="+iid);

String fine_str = ("Fine: Rs. "+fine);

JOptionPane.showMessageDialog(null,fine_str);

}

JOptionPane.showMessageDialog(null,"Book Returned!");

}

catch (SQLException e1) {

// TODO Auto-generated catch block

JOptionPane.showMessageDialog(null, e1);

}

}

});

g.add(l4);

g.add(create_but);

g.add(l1);

g.add(F_iid);

g.add(F_return);

g.setSize(350,250);//400 width and 500 height

g.setLayout(null);//using no layout managers

g.setVisible(true);//making the frame visible

g.setLocationRelativeTo(null);

}

});

f.add(create_but);

f.add(return_book);

f.add(issue_book);

f.add(add_book);

f.add(issued_but);

f.add(users_but);

f.add(view_but);

f.add(add_user);

f.setSize(600,200);//400 width and 500 height

f.setLayout(null);//using no layout managers

f.setVisible(true);//making the frame visible

f.setLocationRelativeTo(null);

}

}