Simple

Exp1:
import java.io.*;
import java.util.Scanner;

class exp1 {
    public static void main(String args[]) throws IOException {
        String choice;
        Scanner d = new Scanner(System.in);
        for(int i = 0;i<2;i++){
        System.out.println("Welcome to the E-mart!");
        }
        int ab = 0;
        while(ab<2){
   System.out.println("Welcome dear customer");
            ab++;
}
        do {
            System.out.print("\nEnter the budget amount: ");
            int a = d.nextInt();
            if (a == 0) {
                System.out.println("Nothing can be purchased for free.");
                System.out.println("Thanks for visiting!");
            } else if (a <= 1200) {
                System.out.println("You can purchase some groceries and some clothes.");
            } else if( a>1200 && a<=2000){
                System.out.println("You can purchase shoes and ties");
            } else if(a>2000 && a<=3000){
System.out.println(" You can buy some suits");
            } else {
                System.out.println("Items are being added");
                System.out.println("Thanks for visiting");
            }
            d.nextLine();
            System.out.print("Enter if you want to order? (Y/N): ");
            choice = d.nextLine();
        } while (choice.equalsIgnoreCase("y"));
        d.close();
    }
}

Exp2:
//switch cases
import java.util.Scanner;

public class exp2 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("Welcome to the E-Commerce Store!");
        System.out.println("Select a product to view its price:");
        System.out.println("1. Laptop");
        System.out.println("2. Smartphone");
        System.out.println("3. Headphones");
        System.out.println("4. Exit");

        int choice;
        do {
            System.out.print("Enter your choice (1-4): ");
            choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    System.out.println("Laptop: $800");
                    break;
                case 2:
                    System.out.println("Smartphone: $500");
                    break;
                case 3:
                    System.out.println("Headphones: $50");
                    break;
                case 4:
                    System.out.println("Thank you for visiting the store!");
                    break;
                default:
                    System.out.println("Invalid choice. Please enter a valid option.");
            }
        } while (choice != 4);

        scanner. Close();
    }
}

Exp3:
//arrays
import java.io.*;
import java.util.Scanner;

class exp3 {
    public static void main(String args[]) throws IOException {
        Scanner d = new Scanner(System.in);
        String num[] = {"Soap", "Pencil", "Notebook", "Detergent(1 Kg)", "Pen", "Clothes"};

        System.out.println("Item present in List");
        for (int i = 0; i < num.length; i++) {
            System.out.println((i + 1) + ". " + num[i]);
        }

        System.out.print("Enter how many items you want to add: ");
        int m = d.nextInt();
        d.nextLine();

        String arr[][] = new String[m][2];
        for (int j = 0; j < m; j++) {
            System.out.print("Enter the item " + (j + 1) + ": ");
            arr[j][0] = d.nextLine();
            System.out.print("Enter the quantity: ");
            arr[j][1] = d.nextLine();
        }

        boolean itemsMatch = true;
        for (int j = 0; j < m; j++) {
            boolean found = false;
            for (int i = 0; i < num.length; i++) {
                if (arr[j][0].equalsIgnoreCase(num[i])) {
                    found = true;
                    break;
                }
            }
            if (!found) {
                itemsMatch = false;
                break;
            }
        }

        if (itemsMatch) {
            System.out.println("\nYour item\tQuantity\tPrice");
            for (int j = 0; j < m; j++) {
                double price = calculatePrice(arr[j][0].toLowerCase(), Integer.parseInt(arr[j][1]));
                System.out.println(arr[j][0] + "\t\t" + arr[j][1] + "\t\t$" + price);
            }
        } else {
            System.out.println("Your item list doesn't match with the items in the store.");
        }
            d.close();
    }

    private static double calculatePrice(String item, int quantity) {
        double pricePerUnit;
        switch (item) {
            case "soap":
                pricePerUnit = 1.0;
                break;
            case "pencil":
                pricePerUnit = 0.5;
                break;
            case "notebook":
                pricePerUnit = 2.0;
                break;
            case "detergent(1 kg)":
                pricePerUnit = 3.5;
                break;
            case "pen":
                pricePerUnit = 1.2;
                break;
            case "clothes":
                pricePerUnit = 10.0;
                break;
            default:
                pricePerUnit = 0.0; // Item not found in the list
        }

        return pricePerUnit * quantity;
    }
}

Exp4:
//method and constructor overloading
class Product{
      String name;
      double price;
      Product(String name,double price){
              this.name=name;
              this.price=price;
      }
      String getname(){
               return name;
      }
      double getprice(){
               return price;
      }
      void display(){
               System.out.println("Product: "+name);
               System.out.println("Price: $"+price);
}
}
class shopc{
      int icount;
      double tamount;
      shopc(){
           icount=0;
           tamount=0.0;
      }
      void addc(Product product){
           icount++;
           tamount+=product.getprice();
           System.out.println(product.getname()+" added to cart");
      }
      void addc(Product product,int qty){
           icount+=qty;
           tamount+=product.getprice()*qty;
           System.out.println(qty+""+product.getname()+" added to cart");
      }
      float display(int a, float b){
           /*System.out.println("Shopping Cart:");
           System.out.println("Total Items: " + icount);
           System.out.println("Total Amount: $" + tamount);*/
           return (a+b);
      }
}
class exp4{
      public static void main(String args[]){
             Product laptop = new Product("Laptop",1000.0);
             Product phone = new Product("Smartphone",500.0);
             shopc cart = new shopc();
             cart.addc(laptop);
             cart.addc(phone,2);
             System.out.println(cart.display(12,(float)32.5));
}
}

Exp5:
//exception handling
import java.util.Scanner;

class Billing {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("Enter the bill amount: ");
        double billAmount = scanner.nextDouble();

        System.out.print("Enter your credit card number: ");
        String cardNumber = scanner.next();

        try {
            validateCreditCard(cardNumber);
            processPayment(billAmount);
            System.out.println("Payment successful. Thank you for shopping!");
        } catch (InvalidCreditCardException e) {
            System.out.println("Payment failed: " + e.getMessage());
        }
        scanner.close();
    }

    static void validateCreditCard(String cardNumber) throws InvalidCreditCardException {
        if (cardNumber.length() > 16) {
            throw new InvalidCreditCardException("Card number is too long.");
        }

        if (!isVisaOrMastercard(cardNumber)) {
            throw new InvalidCreditCardException("Card not issued by Visa/Mastercard.");
        }
    }

    static boolean isVisaOrMastercard(String cardNumber) {
        // You can implement your card type detection logic here.
        // For simplicity, we assume Visa and Mastercard numbers start with 4 and 5.
        return cardNumber.startsWith("4") || cardNumber.startsWith("5");
    }

    static void processPayment(double amount) {
        // This method would process the payment, but for this example, we'll just print a message.
        System.out.println("Processing payment of $" + amount);
    }
}

class InvalidCreditCardException extends Exception {
    public InvalidCreditCardException(String message) {
        super(message);
    }
}

Exp6:
//packages
//main driver code
package Packages;

public class ecommerce {
    public static void main(String[] args) {
        // Create some sample products
        Product product1 = new Product(101, "Laptop", 799.99);
        Product product2 = new Product(102, "Smartphone", 299.99);
        Product product3 = new Product(103, "Headphones", 49.99);

        // Create a shopping cart
        ShoppingCart cart = new ShoppingCart();

        // Add products to the cart
        cart.addProduct(product1, 2);
        cart.addProduct(product2, 1);
        cart.addProduct(product3, 3);

        // Display the contents of the shopping cart
        System.out.println("Shopping Cart Contents:");
        cart.displayCart();

        // Create an order from the shopping cart
        Order order = new Order(cart);

        // Display the order details
        System.out.println("\nOrder Details:");
        order.displayOrder();
    }
}

//package - separate file
package Packages;

import java.util.Date;

public class Order {
    private ShoppingCart cart;
    private Date orderDate;

    public Order(ShoppingCart cart) {
        this.cart = cart;
        this.orderDate = new Date();
    }

    public void displayOrder() {
        System.out.print("Order Date: " + orderDate);
        System.out.println("\n");
        System.out.println("Order Items:");
        cart.displayCart();
    }
}

//package
package Packages;

public class Product {
    private int id;
    private String name;
    private double price;

    public Product(int id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    // Getters and setters for id, name, and price

    public String toString() {
        return name + " (ID: " + id + ", Price: Rs. " + price + ")";
    }
}

//package
package Packages;

import java.util.HashMap;
import java.util.Map;

public class ShoppingCart {
    private Map<Product, Integer> items;

    public ShoppingCart() {
        items = new HashMap<>();
    }

    public void addProduct(Product product, int quantity) {
        items.put(product, quantity);
    }

    public void displayCart() {
        for (Map.Entry<Product, Integer> entry : items.entrySet()) {
            Product product = entry.getKey();
            int quantity = entry.getValue();
            System.out.println(product + " x" + quantity);
        }
    }
}

Master (except packages):
import java.util.Scanner;

public class ECommerceDemo {

    // 1. Entry Exit Control Loop
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int choice;

        do {
            System.out.println("E-Commerce Application Menu");
            System.out.println("1. Browse Products");
            System.out.println("2. Add to Cart");
            System.out.println("3. View Cart");
            System.out.println("4. Checkout");
            System.out.println("5. Exit");

            System.out.print("Enter your choice: ");
            choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    browseProducts();
                    break;
                case 2:
                    addToCart();
                    break;
                case 3:
                    viewCart();
                    break;
                case 4:
                    checkout();
                    break;
                case 5:
                    System.out.println("Exiting the application.");
                    break;
                default:
                    System.out.println("Invalid choice. Please try again.");
            }
        } while (choice != 5);
    }

    // 2. Switch Case with Nested Switch Case
    static void browseProducts() {
        System.out.println("Browse Products Menu");
        System.out.println("1. Electronics");
        System.out.println("2. Clothing");
        System.out.println("3. Back to Main Menu");

        Scanner scanner = new Scanner(System.in);
        int choice = scanner.nextInt();

        switch (choice) {
            case 1:
                System.out.println("Electronics Section");
                break;
            case 2:
                System.out.println("Clothing Section");
                break;
            case 3:
                System.out.println("Returning to the Main Menu");
                break;
            default:
                System.out.println("Invalid choice. Please try again.");
        }
    }

    // 3. Arrays - 1D and 2D
    static void viewCart() {
        String[] cartItems = {"Laptop", "T-Shirt", "Headphones", "Shoes"};

        System.out.println("Items in Your Cart:");
        for (String item : cartItems) {
            System.out.println(item);
        }

        int[][] itemQuantities = {{2, 1}, {3, 2}, {1, 1}, {2, 2}};

        System.out.println("Quantity of Items in Your Cart:");
        for (int i = 0; i < cartItems.length; i++) {
            System.out.println(cartItems[i] + ": " + itemQuantities[i][0] + " items, " + itemQuantities[i][1] + " in stock");
        }
    }

    // 4. Constructor & Method Overloading
    static void addToCart() {
        String product = "Laptop";
        int quantity = 2;
        String seller = "E-Store Inc";

        addToCart(product, quantity);
        addToCart(product, quantity, seller);
    }

    static void addToCart(String product, int quantity) {
        System.out.println(quantity + " " + product + "(s) added to your cart.");
    }

    static void addToCart(String product, int quantity, String seller) {
        System.out.println(quantity + " " + product + "(s) from " + seller + " added to your cart.");
    }

    // 5. Exception Handling
    static void checkout() {
        try {
            // Simulate a checkout process
            int totalAmount = 1000;
            int availableBalance = 800;
            int remainingBalance = totalAmount - availableBalance;

            if (remainingBalance > 0) {
                throw new InsufficientBalanceException("Insufficient balance! You need $" + remainingBalance + " more.");
            } else {
                System.out.println("Checkout successful. Your order has been placed.");
            }
        } catch (InsufficientBalanceException e) {
            System.err.println("Error: " + e.getMessage());
        }
    }
}

class InsufficientBalanceException extends Exception {
    public InsufficientBalanceException(String message) {
        super(message);
    }
}