Main_OOPS.java

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import java.io.FileWriter;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Scanner;
import java.io.File;

// Parent Expense class
class Expense {
    double amount;
    String category;

    public Expense(double amount, String category) {
        this.amount = amount;
        this.category = category;
    }

    @Override
    public String toString() {
        return "Amount: " + amount + ", Category: " + category;
    }
}

// Subclasses for different expense categories
class HomeExpense extends Expense {
    public HomeExpense(double amount) {
        super(amount, "Home");
    }
}

class BillsExpense extends Expense {
    public BillsExpense(double amount) {
        super(amount, "Bills");
    }
}

class HealthExpense extends Expense {
    public HealthExpense(double amount) {
        super(amount, "Health");
    }
}

class EducationExpense extends Expense {
    public EducationExpense(double amount) {
        super(amount, "Education");
    }
}

class TransportationExpense extends Expense {
    public TransportationExpense(double amount) {
        super(amount, "Transportation");
    }
}

class FoodExpense extends Expense {
    public FoodExpense(double amount) {
        super(amount, "Food");
    }
}

// Parent Income class
class Income {
    double amount;
    String category;

    public Income(double amount, String category) {
        this.amount = amount;
        this.category = category;
    }

    @Override
    public String toString() {
        return "Amount: " + amount + ", Category: " + category;
    }
}

// Subclasses for different Income categories
class Refund extends Income {
    public Refund(double amount) {
        super(amount, "Refund");
    }
}

class Grant extends Income {
    public Grant(double amount) {
        super(amount, "Grant");
    }
}

class Salary extends Income {
    public Salary(double amount) {
        super(amount, "Salary");
    }
}

class Sale extends Income {
    public Sale(double amount) {
        super(amount, "Sale");
    }
}

class Award extends Income {
    public Award(double amount) {
        super(amount, "Awards");
    }
}

class Coupon extends Income {
    public Coupon(double amount) {
        super(amount, "Coupon");
    }
}

public class Main {
    private static final String EXPENSES_DIRECTORY = "Expenses/";
    private static final String EXPENSES_FILENAME = EXPENSES_DIRECTORY + "Shrijan_expenses.json";
    private static final String INCOMES_FILENAME = "Shrijan_incomes.json";
    private static final Gson gson = new GsonBuilder().setPrettyPrinting().create();

    private static final String[] FRIENDS = {"Keshav", "Vaibhav", "Praveen", "Ayush", "Harsh"};
    private static final String[] FRIENDS_EXPENSE_FILES = {"Keshav_expenses.json", "Vaibhav_expenses.json",
            "Praveen_expenses.json", "Ayush_expenses.json", "Harsh_expenses.json"};
    private static final String[] FRIENDS_INCOME_FILES = {"Keshav_incomes.json", "Vaibhav_incomes.json",
            "Praveen_incomes.json", "Ayush_incomes.json", "Harsh_incomes.json"};
    private static final Gson[] FRIENDS_EXPENSE_GSON = new Gson[FRIENDS.length];
    private static final Gson[] FRIENDS_INCOME_GSON = new Gson[FRIENDS.length];

    public static void main(String[] args) {
        // Create Expenses directory if it doesn't exist
        File expensesDir = new File(EXPENSES_DIRECTORY);
        if (!expensesDir.exists()) {
            expensesDir.mkdir();
        }

        for (int i = 0; i < FRIENDS.length; i++) {
            FRIENDS_EXPENSE_GSON[i] = new GsonBuilder().setPrettyPrinting().create();
            FRIENDS_INCOME_GSON[i] = new GsonBuilder().setPrettyPrinting().create();
        }
        List<Expense> expenses = loadExpenses();
        List<Income> incomes = loadIncomes();
        Scanner scanner = new Scanner(System.in);

        System.out.println("1. Add an Expense");
        System.out.println("2. Add an Income");
        System.out.println("3. Split Bill");
        System.out.println("4. Display Expenses");
        System.out.println("5. Display Incomes");
        System.out.println("6. Exit");

        while (true) {
            System.out.print("Enter your choice: ");
            int choice = scanner.nextInt();
            scanner.nextLine(); // Consume newline

            switch (choice) {
                case 1:
                    addExpense(scanner, expenses);
                    break;
                case 2:
                    addIncome(scanner, incomes);
                    break;
                case 3:
                    splitBill(scanner, expenses);
                    break;
                case 4:
                    displayExpenses(expenses);
                    break;
                case 5:
                    displayIncomes(incomes);
                    break;
                case 6:
                    System.out.println("Exiting...");
                    scanner.close();
                    return;
                default:
                    System.out.println("Invalid choice. Please enter again.");
            }
        }
    }

    private static void addExpense(Scanner scanner, List<Expense> expenses) {
        System.out.print("Enter the amount: ");
        double amount = scanner.nextDouble();
        scanner.nextLine(); // Consume newline

        System.out.println("Select a category:");
        System.out.println("1. Home");
        System.out.println("2. Bills");
        System.out.println("3. Health");
        System.out.println("4. Education");
        System.out.println("5. Transportation");
        System.out.println("6. Food");

        System.out.print("Enter the category number: ");
        int categoryChoice = scanner.nextInt();
        scanner.nextLine(); // Consume newline
        String category;
        switch (categoryChoice) {
            case 1:
                category = "Home";
                break;
            case 2:
                category = "Bills";
                break;
            case 3:
                category = "Health";
                break;
            case 4:
                category = "Education";
                break;
            case 5:
                category = "Transportation";
                break;
            case 6:
                category = "Food";
                break;
            default:
                System.out.println("Invalid category choice");
                return;
        }
        Expense newExpense = new Expense(amount, category);
        expenses.add(newExpense);
        saveExpenses(expenses);
        System.out.println("Expense added successfully.");
    }

    private static void addIncome(Scanner scanner, List<Income> incomes) {
        System.out.print("Enter the amount: ");
        double amount = scanner.nextDouble();
        scanner.nextLine(); // Consume newline

        System.out.println("Select an income category:");
        System.out.println("1. Refund");
        System.out.println("2. Grant");
        System.out.println("3. Salary");
        System.out.println("4. Sale");
        System.out.println("5. Award");
        System.out.println("6. Coupon");

        System.out.print("Enter the category number: ");
        int categoryChoice = scanner.nextInt();
        scanner.nextLine(); // Consume newline
        String category;
        switch (categoryChoice) {
            case 1:
                category = "Refund";
                break;
            case 2:
                category = "Grant";
                break;
            case 3:
                category = "Salary";
                break;
            case 4:
                category = "Sale";
                break;
            case 5:
                category = "Award";
                break;
            case 6:
                category = "Coupon";
                break;
            default:
                System.out.println("Invalid category choice");
                return;
        }
        Income newIncome = new Income(amount, category);
        incomes.add(newIncome);
        saveIncomes(incomes);
        System.out.println("Income added successfully.");
    }

    private static void splitBill(Scanner scanner, List<Expense> expenses) {
        System.out.print("Enter the amount to split: ");
        double amount = scanner.nextDouble();
        scanner.nextLine(); // Consume newline

        List<String> selectedFriends = selectFriends(scanner);

        double splitAmount = amount / (selectedFriends.size() + 1); // Including yourself
        for (String friend : selectedFriends) {
            int index = Arrays.asList(FRIENDS).indexOf(friend);
            if (index != -1) {
                List<Expense> friendExpenses = loadFriendExpenses(index);
                friendExpenses.add(new Expense(splitAmount, "Shared"));
                saveFriendExpenses(index, friendExpenses);
                System.out.println("Split amount added to " + friend + "'s expenses.");
            }
        }
        expenses.add(new Expense(splitAmount, "Shared"));
        saveExpenses(expenses);
        System.out.println("Split amount added to your expenses.");
    }

    private static List<String> selectFriends(Scanner scanner) {
        List<String> selectedFriends = new ArrayList<>();
        System.out.println("Select friends to split bill with:");
        for (int i = 0; i < FRIENDS.length; i++) {
            System.out.println((i + 1) + ". " + FRIENDS[i]);
        }
        System.out.println("Enter the numbers separated by spaces (e.g., '1 3 4'), or '0' to split with everyone:");
        String input = scanner.nextLine();
        String[] numbers = input.split(" ");
        for (String number : numbers) {
            int index = Integer.parseInt(number) - 1;
            if (index >= 0 && index < FRIENDS.length) {
                selectedFriends.add(FRIENDS[index]);
            }
        }
        return selectedFriends;
    }

    private static void saveExpenses(List<Expense> expenses) {
        try (FileWriter writer = new FileWriter(EXPENSES_FILENAME)) {
            gson.toJson(expenses, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static List<Expense> loadExpenses() {
        try (FileReader reader = new FileReader(EXPENSES_FILENAME)) {
            Expense[] expensesArray = gson.fromJson(reader, Expense[].class);
            if (expensesArray != null) {
                return new ArrayList<>(List.of(expensesArray));
            }
        } catch (IOException e) {
            // If file does not exist or cannot be read, return an empty list
        }
        return new ArrayList<>();
    }

    private static void saveFriendExpenses(int index, List<Expense> expenses) {
        String friendExpensesFilename = EXPENSES_DIRECTORY + FRIENDS_EXPENSE_FILES[index];
        try (FileWriter writer = new FileWriter(friendExpensesFilename)) {
            FRIENDS_EXPENSE_GSON[index].toJson(expenses, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static List<Expense> loadFriendExpenses(int index) {
        String friendExpensesFilename = EXPENSES_DIRECTORY + FRIENDS_EXPENSE_FILES[index];
        try (FileReader reader = new FileReader(friendExpensesFilename)) {
            Expense[] expensesArray = FRIENDS_EXPENSE_GSON[index].fromJson(reader, Expense[].class);
            if (expensesArray != null) {
                return new ArrayList<>(List.of(expensesArray));
            }
        } catch (IOException e) {
            // If file does not exist or cannot be read, return an empty list
        }
        return new ArrayList<>();
    }

    private static void saveIncomes(List<Income> incomes) {
        try (FileWriter writer = new FileWriter(INCOMES_FILENAME)) {
            gson.toJson(incomes, writer);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private static List<Income> loadIncomes() {
        try (FileReader reader = new FileReader(INCOMES_FILENAME)) {
            Income[] incomesArray = gson.fromJson(reader, Income[].class);
            if (incomesArray != null) {
                return new ArrayList<>(List.of(incomesArray));
            }
        } catch (IOException e) {
            // If file does not exist or cannot be read, return an empty list
        }
        return new ArrayList<>();
    }

    private static void displayExpenses(List<Expense> expenses) {
        if (expenses.isEmpty()) {
            System.out.println("No expenses recorded.");
            return;
        }
        System.out.println("Expenses:");
        for (Expense expense : expenses) {
            System.out.println(expense);
        }
    }

    private static void displayIncomes(List<Income> incomes) {
        if (incomes.isEmpty()) {
            System.out.println("No incomes recorded.");
            return;
        }
        System.out.println("Incomes:");
        for (Income income : incomes) {
            System.out.println(income);
        }
    }
}