What data storage methods do you know?

1. SharedPreferences: For storing simple key-value pairs (primitive types). Fast access, but not suitable for large data volumes.

2. Internal Storage: File system accessible only to the app. Data is deleted upon uninstallation. Suitable for private data.

   // Writing a file
   applicationContext.openFileOutput("my_file.txt", Context.MODE_PRIVATE).use {
       it.write("Some data".toByteArray())
   }
   
   // Reading a file
   applicationContext.openFileInput("my_file.txt").bufferedReader().useLines { lines ->
       lines.forEach { println(it) }
   }
   

3. External Storage: File system accessible to other apps (with permissions) and the user. Data persists after uninstallation. Requires attention to permissions on Android 10+. Suitable for non-sensitive data.

4. SQLite Databases: Relational database. Suitable for structured data requiring complex queries. Requires more code to implement. Room Persistence Library is the recommended ORM.

   -- Example SQL query
   SELECT * FROM users WHERE age > 30
   

5. Content Providers: Provide structured access to shared data sets. Can be created for your own data or used to access data from other apps (e.g., contacts).

6. DataStore: Modern asynchronous solution for data storage, replacing SharedPreferences and part of SQLite functionality. Comes in two types: Preferences DataStore (for key-value pairs) and Proto DataStore (for typed objects with Protobuf).

   // Preferences DataStore example
   val Context.dataStore: DataStore<Preferences> by preferencesDataStore(name = "settings")
   
   suspend fun saveSetting(context: Context, key: String, value: Boolean) {
       context.dataStore.edit { settings ->
           settings[booleanPreferencesKey(key)] = value
       }
   }
   

7. Jetpack DataStore (earlier versions) / DataSync / other cloud solutions: For synchronizing data between user devices and storing backups. Requires integration with cloud services.

The choice of method depends on the data type, volume, need for shared access, security considerations, and performance requirements.