Small wrapper for shared preferences.

ObjectSaver.java

// build.gradle
// implementation 'com.google.code.gson:gson:2.8.1'

public class ObjectSaver {
    private static SharedPreferences sharedPreferences;
    private static Resources resources;
    private static Gson gson;

    public static void init(Context context) {
        sharedPreferences = PreferenceManager.getDefaultSharedPreferences(context);
        resources = context.getResources();
        gson = new Gson();
    }

    public static void put(String key, Object o){
        sharedPreferences.edit()
                .putString(key, gson.toJson(o))
                .apply();
    }

    public static void put(int resKey, Object o){
        put(resources.getString(resKey), o);
    }

    public static <T> T get(String key, Class<T> type){
        return gson.fromJson(sharedPreferences.getString(key, null), type);
    }

    public static <T> T get(int resKey, Class<T> type){
        return get(resources.getString(resKey), type);
    }
}

// Initialize one time
public class MyApp extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        ObjectSaver.init(this);
    }
}

// Then use whenever you want
public void somewhere(){
    ObjectSaver.put("object", new User("Omar", 19));
    User user = ObjectSaver.get("object", User.class);
}