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);
}
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=string");
//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);
}
}
Write, Run & Share Java code online using OneCompiler's Java online compiler for free. It's one of the robust, feature-rich online compilers for Java language, running the Java LTS version 17. Getting started with the OneCompiler's Java editor is easy and fast. The editor shows sample boilerplate code when you choose language as Java and start coding.
OneCompiler's Java online editor supports stdin and users can give inputs to the programs using the STDIN textbox under the I/O tab. Using Scanner class in Java program, you can read the inputs. Following is a sample program that shows reading STDIN ( A string in this case ).
import java.util.Scanner;
class Input {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter your name: ");
String inp = input.next();
System.out.println("Hello, " + inp);
}
}
OneCompiler supports Gradle for dependency management. Users can add dependencies in the build.gradle file and use them in their programs. When you add the dependencies for the first time, the first run might be a little slow as we download the dependencies, but the subsequent runs will be faster. Following sample Gradle configuration shows how to add dependencies
apply plugin:'application'
mainClassName = 'HelloWorld'
run { standardInput = System.in }
sourceSets { main { java { srcDir './' } } }
repositories {
jcenter()
}
dependencies {
// add dependencies here as below
implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.9'
}
Java is a very popular general-purpose programming language, it is class-based and object-oriented. Java was developed by James Gosling at Sun Microsystems ( later acquired by Oracle) the initial release of Java was in 1995. Java 17 is the latest long-term supported version (LTS). As of today, Java is the world's number one server programming language with a 12 million developer community, 5 million students studying worldwide and it's #1 choice for the cloud development.
short x = 999; // -32768 to 32767
int x = 99999; // -2147483648 to 2147483647
long x = 99999999999L; // -9223372036854775808 to 9223372036854775807
float x = 1.2;
double x = 99.99d;
byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
// code
} else {
// code
}
Example:
int i = 10;
if(i % 2 == 0) {
System.out.println("i is even number");
} else {
System.out.println("i is odd number");
}
Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.
switch(<conditional-expression>) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
//code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(<condition>){
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (<condition>);
Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.
class keyword is required to create a class.
class Mobile {
public: // access specifier which specifies that accessibility of class members
string name; // string variable (attribute)
int price; // int variable (attribute)
};
Mobile m1 = new Mobile();
public class Greeting {
static void hello() {
System.out.println("Hello.. Happy learning!");
}
public static void main(String[] args) {
hello();
}
}
Collection is a group of objects which can be represented as a single unit. Collections are introduced to bring a unified common interface to all the objects.
Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:
This framework also defines map interfaces and several classes in addition to Collections.
| Collection | Description |
|---|---|
| Set | Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc |
| List | List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors |
| Queue | FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue. |
| Deque | Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail) |
| Map | Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc. |