SQLite Model class

DatabaseHelper.java

// A helper class to work with SQLite database
public class DatabaseHelper extends SQLiteOpenHelper {
    // Database version, which should be upgraded each time we made changes in database structure
    private static final int DATABASE_VERSION = 1;

    // Database name
    private static final String DATABASE_NAME = "notes_db";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // Creating tables
    @Override
    public void onCreate(SQLiteDatabase db) {

        // create notes table
        db.execSQL(Note.CREATE_TABLE);
    }

    // Upgrading database
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop (or delete) older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + Note.TABLE_NAME);

        // Create tables again
        onCreate(db);
    }

    public long insertNote(String note) {
        // get writable database as we want to write data
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        // `id` and `timestamp` will be inserted automatically.
        // no need to add them
        values.put(Note.COLUMN_NOTE, note);

        // insert row
        long id = db.insert(Note.TABLE_NAME, null, values);

        // close db connection
        db.close();

        // return newly inserted row id
        return id;
    }

    public Note getNote(long id) {
        // get readable database as we are not inserting anything
        SQLiteDatabase db = this.getReadableDatabase();

        // creating a Cursor object to be able to lookup the table
        Cursor cursor = db.query(Note.TABLE_NAME,
                new String[]{Note.COLUMN_ID, Note.COLUMN_NOTE, Note.COLUMN_TIMESTAMP},
                Note.COLUMN_ID + "=?",
                new String[]{String.valueOf(id)}, null, null, null, null);

        if (cursor != null)
            cursor.moveToFirst();

        // prepare note object
        Note note = new Note(
                cursor.getInt(cursor.getColumnIndex(Note.COLUMN_ID)),
                cursor.getString(cursor.getColumnIndex(Note.COLUMN_NOTE)),
                cursor.getString(cursor.getColumnIndex(Note.COLUMN_TIMESTAMP)));

        // close the db connection
        cursor.close();

        return note;
    }

    public List<Note> getAllNotes() {
        List<Note> notes = new ArrayList<>();

        // query to select all the data from the notes table
        String selectQuery = "SELECT * FROM " + Note.TABLE_NAME + " ORDER BY " +
                Note.COLUMN_TIMESTAMP + " DESC";

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Note note = new Note();
                note.setId(cursor.getInt(cursor.getColumnIndex(Note.COLUMN_ID)));
                note.setNote(cursor.getString(cursor.getColumnIndex(Note.COLUMN_NOTE)));
                note.setTimestamp(cursor.getString(cursor.getColumnIndex(Note.COLUMN_TIMESTAMP)));

                notes.add(note);
            } while (cursor.moveToNext());
        }

        // close db connection
        db.close();

        // return notes list
        return notes;
    }

    public int getNotesCount() {
        String countQuery = "SELECT  * FROM " + Note.TABLE_NAME;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);

        int count = cursor.getCount();
        cursor.close();

        // return count
        return count;
    }

    public int updateNote(Note note) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(Note.COLUMN_NOTE, note.getNote());

        // updating row
        int row = db.update(Note.TABLE_NAME, values, Note.COLUMN_ID + " = ?",
                new String[]{String.valueOf(note.getId())});
        
        db.close();
        
        return row;
    }

    public void deleteNote(Note note) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete(Note.TABLE_NAME, Note.COLUMN_ID + " = ?",
                new String[]{String.valueOf(note.getId())});
        db.close();
    }
}

Note.java

public class Note {
    // The name of table which will be created in the database
    public static final String TABLE_NAME = "notes";

    // The names of columns which will be in our table
    public static final String COLUMN_ID = "id";
    public static final String COLUMN_NOTE = "note";
    public static final String COLUMN_TIMESTAMP = "timestamp";

    // Class members of model according to table
    private int id;
    private String note;
    private String timestamp;


    // An SQL query to create a table with given columns
    public static final String CREATE_TABLE =
            "CREATE TABLE " + TABLE_NAME + "("
                    + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," // PRIMARY KEY for uniqueness and AUTOINCREMENT to grow value each time by 1
                    + COLUMN_NOTE + " TEXT,"
                    + COLUMN_TIMESTAMP + " DATETIME DEFAULT CURRENT_TIMESTAMP" // take current time
                    + ")";

    // A primary constructor
    public Note() {
    }
    
    // A constructor with parameters
    public Note(int id, String note, String timestamp) {
        this.id = id;
        this.note = note;
        this.timestamp = timestamp;
    }

    // Getters and setters
    public int getId() {
        return id;
    }

    public String getNote() {
        return note;
    }

    public void setNote(String note) {
        this.note = note;
    }

    public String getTimestamp() {
        return timestamp;
    }

    public void setId(int id) {
        this.id = id;
    }

    public void setTimestamp(String timestamp) {
        this.timestamp = timestamp;
    }
}