TrackifyCore.java

import java.io.*;
import java.util.*;

class Expense {
    double amount;
    String category;
    String date;

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

    public String toString() {
        return amount + "," + category + "," + date;
    }
}

public class TrackifyCore {

    static ArrayList<Expense> expenses = new ArrayList<>();
    static final String FILE_NAME = "expenses.txt";

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

        loadExpenses();

        while (true) {
            System.out.println("\n1. Add Expense");
            System.out.println("2. View Expenses");
            System.out.println("3. Exit");

            int choice = sc.nextInt();

            switch (choice) {
                case 1:
                    addExpense(sc);
                    break;
                case 2:
                    viewExpenses();
                    break;
                case 3:
                    saveExpenses();
                    System.out.println("Exiting...");
                    return;
                default:
                    System.out.println("Invalid choice");
            }
        }
    }

    static void addExpense(Scanner sc) {
        try {
            System.out.print("Enter amount: ");
            double amount = sc.nextDouble();
            sc.nextLine();

            System.out.print("Enter category: ");
            String category = sc.nextLine();

            System.out.print("Enter date: ");
            String date = sc.nextLine();

            Expense exp = new Expense(amount, category, date);
            expenses.add(exp);

            System.out.println("Expense Added!");

        } catch (Exception e) {
            System.out.println("Invalid input!");
        }
    }

    static void viewExpenses() {
        if (expenses.isEmpty()) {
            System.out.println("No expenses found.");
            return;
        }

        for (Expense e : expenses) {
            System.out.println(e.amount + " | " + e.category + " | " + e.date);
        }
    }

    static void saveExpenses() {
        try (PrintWriter pw = new PrintWriter(new FileWriter(FILE_NAME))) {
            for (Expense e : expenses) {
                pw.println(e);
            }
        } catch (IOException e) {
            System.out.println("Error saving file");
        }
    }

    static void loadExpenses() {
        try (BufferedReader br = new BufferedReader(new FileReader(FILE_NAME))) {
            String line;
            while ((line = br.readLine()) != null) {
                String[] data = line.split(",");
                expenses.add(new Expense(
                        Double.parseDouble(data[0]),
                        data[1],
                        data[2]
                ));
            }
        } catch (IOException e) {
            System.out.println("No previous data found.");
        }
    }
}