@PreferenceEntity("UserProfile")
public class Profile {
    protected final boolean login = false;
    @KeyName("nickname") protected final String userNickName = null;
    @KeyName("visits") protected final int visitCount = 1;

    @KeyName("userPet")
    @TypeConverter(PetConverter.class)
    protected Pet userPetInfo;

    @PreferenceFunction("nickname")
    public String putUserNickFunction(String nickname) {
        return "Hello, " + nickname;
    }

    @PreferenceFunction("nickname")
    public String getUserNickFunction(String nickname) {
        return nickname + "!!!";
    }

    @PreferenceFunction("visits")
    public int putVisitCountFunction(int count) {
        return ++count;
    }
}

Preference_UserProfile userProfile = Preference_UserProfile.getInstance(this); // gets instance of the UserProfile entity.
userProfile.putNickname("my nickname"); // puts a value in NickName.
userProfile.getNickname(); // gets a nickname value.
userProfile.containsNickname(); // checks nickname key value is exist or not in entity.
userProfile.removeNickname(); // removes nickname key value in entity.
userProfile.nicknameKeyName(); // returns nickname key name.
userProfile.getEntityName(); // returns UserProfile entity name;
userProfile.getkeyNameList(); // returns UserProfile entity's key name lists.

// or invoke static.
Preference_UserProfile.getInstance(this).putNickname("my nickname");

userProfile.addNicknameOnChangedListener(new Preference_UserProfile.NicknameOnChangedListener() {
   @Override
   public void onChanged(String nickname) {
     Toast.makeText(getBaseContext(), "onChanged :" + nickname, Toast.LENGTH_SHORT).show();
   }
});

@DefaultPreference
@PreferenceEntity("ProfileWithDefault")
public class UserProfilewithDefaultPreference {
    @KeyName("nickname")
    protected final String userNickName = "skydoves";
    
    // key name will be 'Login'. (login's camel uppercase)
    protected final boolean login = false;
}

PreferenceManager.getDefaultSharedPreferences(context);

@KeyName("visits") // keyname will be Visits.
protected final int visitCount = 1;

@TypeConverter(PetConverter.class)
protected Pet userPetInfo; // 'Pet' class field in an entity.

public class PetConverter extends PreferenceTypeConverter<Pet> {

    private final Gson gson;

    // default constructor will be called by PreferenceRoom
    public PetConverter() {
        this.gson = new Gson();
    }

    @Override
    public String convertObject(Pet pet) {
        return gson.toJson(pet);
    }

    @Override
    public Pet convertType(String string) {
        return gson.fromJson(string, Pet.class);
    }
}

public class BaseGsonConverter<T> extends PreferenceTypeConverter<T> {

    private final Gson gson;

    public BaseGsonConverter(Class<T> clazz) {
        super(clazz);
        this.gson = new Gson();
    }

    @Override
    public String convertObject(T object) {
        return gson.toJson(object);
    }

    @Override
    public T convertType(String string) {
        return gson.fromJson(string, clazz);
    }
}

@KeyName("userinfo")
@TypeConverter(BaseGsonConverter.class)
protected PrivateInfo privateInfo;

@KeyName("userPet")
@TypeConverter(BaseGsonConverter.class)
protected Pet userPetInfo;

@PreferenceFunction("nickname")
public String putUserNickFunction(String nickname) {
    return "Hello, " + nickname;
}

@PreferenceFunction("nickname")
public String getUserNickFunction(String nickname) {
    return nickname + "!!!";
}

@EncryptEntity("1234567890ABCDFG")
@PreferenceEntity("UserProfile")
public class Profile {
}

@PreferenceFunction("uuid")
public String putUuidFunction(String uuid) {
   return SecurityUtils.encrypt(uuid);
}

@PreferenceFunction("uuid")
public String getUuidFunction(String uuid) {
    return SecurityUtils.decrypt(uuid);
}

@PreferenceComponent(entities = {Profile.class, Device.class})
public interface UserProfileComponent {
}

public class MyApplication extends Application {

    @Override
    public void onCreate() {
        super.onCreate();
        PreferenceComponent_UserProfileComponent.init(this);
    }
}

PreferenceComponent_UserProfileComponent component = PreferenceComponent_UserProfileComponent.getInstance();
Preference_UserProfile userProfile = component.UserProfile();
Preference_UserDevice userDevice = PreferenceComponent_UserProfileComponent.getInstance().UserDevice();

@PreferenceComponent(entities = {Profile.class, Device.class})
public interface UserProfileComponent {
    // declares targets for the dependency injection.
    void inject(MainActivity __);
    void inject(LoginActivity __);
}

@InjectPreference
public PreferenceComponent_UserProfileComponent component;

@InjectPreference
public Preference_UserProfile userProfile;

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   setContentView(R.layout.activity_main);
   PreferenceComponent_UserProfileComponent.getInstance().inject(this);
}

@PreferenceEntity("UserDevice")
open class Device {
    @KeyName("version")
    @JvmField val deviceVersion: String? = null

    @KeyName("uuid")
    @JvmField val userUUID: String? = null

    @PreferenceFunction("uuid")
    open fun putUuidFunction(uuid: String?): String? {
        return SecurityUtils.encrypt(uuid)
    }

    @PreferenceFunction( "uuid")
    open fun getUuidFunction(uuid: String?): String? {
        return SecurityUtils.decrypt(uuid)
    }
}

@PreferenceComponent(entities = [Profile::class, Device::class])
interface UserProfileComponent {
    // declare dependency injection targets.
    fun inject(target: MainActivity)
    fun inject(target: LoginActivity)
}

@InjectPreference
lateinit var component: PreferenceComponent_UserProfileComponent
    
override fun onCreate(savedInstanceState: Bundle?) {
   super.onCreate(savedInstanceState)
   setContentView(R.layout.activity_main)
    PreferenceComponent_UserProfileComponent.getInstance().inject(this) // inject dependency injection to MainActivity.