NotesApp.java

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

/**
 * NotesApp - A simple beginner-friendly Java application to demonstrate File I/O.
 * This app allows writing a note to a text file and reading all notes back.
 * 
 * Author: Mummana Devi Prasad
 */
public class NotesApp {

    // The name of the file where notes will be stored
    private static final String FILE_NAME = "notes.txt";

    /**
     * Writes a note to the file.
     * Use FileWriter to append the note to the end of the file.
     * 
     * @param note The content of the note to be saved.
     */
    public void addNote(String note) {
        // Using try-with-resources to ensure the FileWriter is closed automatically
        try (FileWriter writer = new FileWriter(FILE_NAME, true)) {
            writer.write(note + "\n");
            System.out.println("Success: Note added successfully to " + FILE_NAME);
        } catch (IOException e) {
            System.out.println("Error while writing to file: " + e.getMessage());
        }
    }

    /**
     * Reads and displays all notes from the file.
     * Uses FileReader wrapped in BufferedReader for efficient reading.
     */
    public void readNotes() {
        System.out.println("\n--- All Notes ---");
        // Using try-with-resources for FileReader and BufferedReader
        try (FileReader reader = new FileReader(FILE_NAME);
             BufferedReader bufferedReader = new BufferedReader(reader)) {
            
            String line;
            boolean hasNotes = false;
            
            // Read the file line by line
            while ((line = bufferedReader.readLine()) != null) {
                System.out.println(line);
                hasNotes = true;
            }
            
            if (!hasNotes) {
                System.out.println("No notes found in the file.");
            }
            
        } catch (IOException e) {
            System.out.println("Error while reading from file: " + e.getMessage() + 
                               " (Maybe the file hasn't been created yet?)");
        }
    }

    /**
     * Main method to demonstrate the functionality of the NotesApp.
     */
    public static void main(String[] args) {
        NotesApp myApp = new NotesApp();

        // 1. Adding a sample note
        System.out.println("Adding a sample note...");
        myApp.addNote("Learning Java File I/O is fun!");
        myApp.addNote("Object-Oriented Programming makes code organized.");

        // 2. Reading all notes back
        System.out.println("\nReading all notes from the file...");
        myApp.readNotes();
    }
}