kshokh · kshokh · Oct 21, 2025
diff --git a/lessons/src/main/java/lessons/lesson07/App.java b/lessons/src/main/java/lessons/lesson07/App.java
@@ -0,0 +1,64 @@
+package Lesson7;
+
+import lombok.Cleanup;
+
+import java.util.Scanner;
+
+/**
+ * author Shohjahon
+ * version 1.1
+ */
+
+public class App {
+    public static void main( String[] args ) {
+        SeatManager manager = new SeatManager();
+        @Cleanup Scanner scanner = new Scanner( System.in );
+        int choice;
+
+        do {
+            System.out.println( "\n=== Airline Booking System ===" );
+            System.out.println( "1. View all seats" );
+            System.out.println( "2. Reserve a seat" );
+            System.out.println( "3. Pay for a seat" );
+            System.out.println( "4. Cancel reservation" );
+            System.out.println( "5. View reservation by seat number" );
+            System.out.println( "6. Exit" );
+            System.out.print( "Enter your choice: " );
+
+            try {
+                choice = Integer.parseInt( scanner.nextLine() );
+            } catch ( NumberFormatException e ) {
+                System.out.println( "Invalid input! Enter a number 1–6." );
+                choice = 0;
+            }
+
+            switch ( choice ) {
+                case 1 -> manager.viewAllSeats();
+                case 2 -> {
+                    System.out.print( "Enter seat number (e.g., S5): " );
+                    String seatNumber = scanner.nextLine().trim().toUpperCase();
+                    System.out.print( "Enter passenger name: " );
+                    String name = scanner.nextLine().trim();
+                    manager.reserveSeat( seatNumber, name );
+                }
+                case 3 -> {
+                    System.out.print( "Enter seat number to pay: " );
+                    String seatNumber = scanner.nextLine().trim().toUpperCase();
+                    manager.payForSeat( seatNumber );
+                }
+                case 4 -> {
+                    System.out.print( "Enter seat number to cancel: " );
+                    String seatNumber = scanner.nextLine().trim().toUpperCase();
+                    manager.cancelReservation( seatNumber );
+                }
+                case 5 -> {
+                    System.out.print( "Enter seat number to view: " );
+                    String seatNumber = scanner.nextLine().trim().toUpperCase();
+                    manager.viewReservation( seatNumber );
+                }
+                case 6 -> System.out.println( "Goodbye!" );
+                default -> System.out.println( "Invalid option. Try again." );
+            }
+        } while ( choice != 6 );
+    }
+}
diff --git a/lessons/src/main/java/lessons/lesson07/Seat.java b/lessons/src/main/java/lessons/lesson07/Seat.java
@@ -0,0 +1,65 @@
+package Lesson7;
+
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+import java.io.Serial;
+import java.io.Serializable;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+public class Seat implements Serializable {
+    @Serial
+    private static final long serialVersionUID = 1L;
+
+    private String seatNumber;
+    private String seatClass;
+    private SeatStatus status;
+    private String passengerName;
+    private LocalDateTime bookingTime;
+    private LocalDateTime flightDeparture;
+
+    public void reserve( String name ) {
+        this.passengerName = name;
+        this.status = SeatStatus.BOOKED;
+        this.bookingTime = LocalDateTime.now();
+    }
+
+    public void pay() {
+        this.status = SeatStatus.PAID;
+    }
+
+    public void cancel() {
+        this.passengerName = "";
+        this.status = SeatStatus.AVAILABLE;
+        this.bookingTime = null;
+    }
+
+    public boolean isExpired() {
+        if ( status == SeatStatus.BOOKED && bookingTime != null ) {
+            return bookingTime.plusMinutes( 24 ).isBefore( LocalDateTime.now() );
+        }
+        return false;
+    }
+
+    @Override
+    public String toString() {
+        String bookingInfo = (bookingTime != null)
+                ? bookingTime.format( DateTimeFormatter.ofPattern( "yyyy-MM-dd HH:mm" ) )
+                : "-";
+        String flightInfo = (flightDeparture != null)
+                ? flightDeparture.format( DateTimeFormatter.ofPattern( "yyyy-MM-dd HH:mm" ) )
+                : "-";
+        return String.format( "%-5s | %-10s | %-9s | %-15s | %-16s | %-16s",
+                seatNumber,
+                seatClass,
+                status,
+                passengerName.isEmpty() ? "-" : passengerName,
+                bookingInfo,
+                flightInfo );
+    }
+}
diff --git a/lessons/src/main/java/lessons/lesson07/SeatManager.java b/lessons/src/main/java/lessons/lesson07/SeatManager.java
@@ -0,0 +1,142 @@
+package Lesson7;
+
+import java.io.*;
+import java.time.LocalDateTime;
+import java.util.*;
+
+public class SeatManager {
+    private static final String DATA_FILE = "seats.dat";
+    private ArrayList< Seat > seats;
+
+    public SeatManager() {
+        seats = new ArrayList<>();
+        loadSeats();
+    }
+
+    private void initializeSeats() {
+        for ( int i = 1; i <= 30; i++ ) {
+            String seatClass = (i <= 10) ? "First" : (i <= 20) ? "Business" : "Economy";
+            LocalDateTime flightDate = LocalDateTime.now().plusDays( 1 );
+            seats.add( new Seat( "S" + i, seatClass, SeatStatus.AVAILABLE, "", null, flightDate ) );
+        }
+    }
+
+    private void resetExpiredBookings() {
+        for ( Seat seat : seats ) {
+            if ( seat.isExpired() ) {
+                seat.cancel();
+            }
+        }
+    }
+
+    public void viewAllSeats() {
+        resetExpiredBookings();
+        System.out.println( "\nSeat | Class      | Status    | Passenger       | Booked Time     | Flight Time" );
+        System.out.println( "-------------------------------------------------------------------------------" );
+        for ( Seat seat : seats ) {
+            System.out.println( seat );
+        }
+    }
+
+    public void reserveSeat( String seatNumber, String name ) {
+        Seat seat = findSeat( seatNumber );
+        if ( seat == null ) {
+            System.out.println( "Seat not found!" );
+            return;
+        }
+        if ( seat.getStatus() == SeatStatus.PAID ) {
+            System.out.println( "Seat already paid for by " + seat.getPassengerName() );
+            return;
+        }
+        if ( seat.getStatus() == SeatStatus.BOOKED && !seat.isExpired() ) {
+            System.out.println( "Seat already booked by " + seat.getPassengerName() );
+            return;
+        }
+
+        seat.reserve( name );
+        saveSeats();
+        System.out.println( "Seat " + seatNumber + " successfully reserved for " + name + "." );
+    }
+
+    public void payForSeat( String seatNumber ) {
+        Seat seat = findSeat( seatNumber );
+        if ( seat == null ) {
+            System.out.println( "Seat not found!" );
+            return;
+        }
+        if ( seat.getStatus() != SeatStatus.BOOKED ) {
+            System.out.println( "Seat must be booked first before payment." );
+            return;
+        }
+        seat.pay();
+        saveSeats();
+        System.out.println( "Seat " + seatNumber + " successfully paid for." );
+    }
+
+    public void cancelReservation( String seatNumber ) {
+        Seat seat = findSeat( seatNumber );
+        if ( seat == null ) {
+            System.out.println( "Seat not found!" );
+            return;
+        }
+        if ( seat.getStatus() == SeatStatus.AVAILABLE ) {
+            System.out.println( "Seat is not currently booked." );
+            return;
+        }
+        seat.cancel();
+        saveSeats();
+        System.out.println( "Reservation for seat " + seatNumber + " canceled." );
+    }
+
+    public void viewReservation( String seatNumber ) {
+        resetExpiredBookings();
+        Seat seat = findSeat( seatNumber );
+        if ( seat == null ) {
+            System.out.println( "Seat not found!" );
+            return;
+        }
+
+        System.out.println( "\n--- Seat Details ---" );
+        System.out.println( "Seat Number : " + seat.getSeatNumber() );
+        System.out.println( "Class       : " + seat.getSeatClass() );
+        System.out.println( "Status      : " + seat.getStatus() );
+        System.out.println( "Passenger   : " + (seat.getPassengerName().isEmpty() ? "-" : seat.getPassengerName()) );
+        System.out.println( "Booking Time: " + (seat.getBookingTime() != null ? seat.getBookingTime() : "-") );
+        System.out.println( "Flight Time : " + seat.getFlightDeparture() );
+    }
+
+    private Seat findSeat( String seatNumber ) {
+        for ( Seat seat : seats ) {
+            if ( seat.getSeatNumber().equalsIgnoreCase( seatNumber ) ) {
+                return seat;
+            }
+        }
+        return null;
+    }
+
+    @SuppressWarnings( "unchecked" )
+    private void loadSeats() {
+        File file = new File( DATA_FILE );
+        if ( !file.exists() ) {
+            initializeSeats();
+            saveSeats();
+            return;
+        }
+
+        try ( ObjectInputStream ois = new ObjectInputStream( new FileInputStream( file ) ) ) {
+            seats = ( ArrayList< Seat > ) ois.readObject();
+            System.out.println( "Previous seat data loaded successfully." );
+        } catch ( Exception e ) {
+            System.out.println( "Error loading saved data. Reinitializing seats..." );
+            initializeSeats();
+        }
+    }
+
+    private void saveSeats() {
+        try ( ObjectOutputStream oos = new ObjectOutputStream( new FileOutputStream( DATA_FILE ) ) ) {
+            oos.writeObject( seats );
+        } catch ( IOException e ) {
+            System.out.println( "Error saving seat data: " + e.getMessage() );
+        }
+    }
+}
diff --git a/lessons/src/main/java/lessons/lesson07/SeatStatus.java b/lessons/src/main/java/lessons/lesson07/SeatStatus.java
@@ -0,0 +1,7 @@
+package Lesson7;
+
+public enum SeatStatus {
+    AVAILABLE,
+    BOOKED,
+    PAID
+}