10 Best Java Projects

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

// Complete Todo List CLI Application with file persistence
public class TodoListCLI {
    private static final String FILE_NAME = "todos.txt";
    private static List<String> todos = new ArrayList<>();
    private static Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) {
        loadTodos();
        while (true) {
            System.out.println("\n=== TODO LIST MANAGER ===");
            System.out.println("1. Add Task\n2. View Tasks\n3. Update Task\n4. Delete Task\n5. Exit");
            System.out.print("Choose option: ");
            int choice = scanner.nextInt();
            scanner.nextLine(); // consume newline
            
            switch (choice) {
                case 1: addTask(); break;
                case 2: viewTasks(); break;
                case 3: updateTask(); break;
                case 4: deleteTask(); break;
                case 5: saveTodos(); System.out.println("Goodbye!"); return;
                default: System.out.println("Invalid option!");
            }
        }
    }

    private static void addTask() {
        System.out.print("Enter task: ");
        todos.add(scanner.nextLine());
        System.out.println("Task added!");
    }

    private static void viewTasks() {
        if (todos.isEmpty()) { System.out.println("No tasks!"); return; }
        for (int i = 0; i < todos.size(); i++)
            System.out.println((i + 1) + ". " + todos.get(i));
    }

    private static void updateTask() {
        viewTasks();
        if (todos.isEmpty()) return;
        System.out.print("Task number to update: ");
        int idx = scanner.nextInt() - 1;
        scanner.nextLine();
        if (idx >= 0 && idx < todos.size()) {
            System.out.print("New task: ");
            todos.set(idx, scanner.nextLine());
            System.out.println("Task updated!");
        } else System.out.println("Invalid task number!");
    }

    private static void deleteTask() {
        viewTasks();
        if (todos.isEmpty()) return;
        System.out.print("Task number to delete: ");
        int idx = scanner.nextInt() - 1;
        if (idx >= 0 && idx < todos.size()) {
            todos.remove(idx);
            System.out.println("Task deleted!");
        } else System.out.println("Invalid task number!");
    }

    private static void loadTodos() {
        try (BufferedReader br = new BufferedReader(new FileReader(FILE_NAME))) {
            String line;
            while ((line = br.readLine()) != null) todos.add(line);
        } catch (IOException e) { /* File doesn't exist yet */ }
    }

    private static void saveTodos() {
        try (BufferedWriter bw = new BufferedWriter(new FileWriter(FILE_NAME))) {
            for (String todo : todos) bw.write(todo + "\n");
        } catch (IOException e) { System.err.println("Error saving: " + e.getMessage()); }
    }
}