variosJava.java

/**
* TestTestTest
**/

public class TestTestTest extends Activity {

    public String getMyText() {
        return myText;
    }

    public void setMyText(String myText) {
        this.myText = myText;
    }

    String myText = "Initial Value";

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setMyText("Hello World!");

    }

    public String showText () {
        Log.d("test___", "My Text: " + getMyText());
        return getMyText();
    }
}

/**
* TestModule
**/

public class TestModule extends ReactContextBaseJavaModule {

  TestTestTest test;

    //Constructor
    public TestModule(ReactApplicationContext reactContext) {
        super(reactContext);
    }

    //Module Name
    @Override
    public String getName() { return "TestModule"; }

    @ReactMethod
    public void getMyText (Promise promise) {

        test = new TestTestTest();
        test.showText(); //retorna `Initial Value`
        promise.resolve("Olha o console do Android Studio");
    }
}