Is there any way to enable scrollbars for RecyclerView in code?

Set the vertical scrollbar in the xml layout

<android.support.v7.widget.RecyclerView
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:scrollbars="vertical" />

At the moment it seems to be impossible to enable scroll bars programmatically. The reason for that behaviour is that Android does not call either View.initializeScrollbarsInternal(TypedArray a) or View.initializeScrollbars(TypedArray a). Both methods are only called if you instantiate your RecyclerView with an AttributeSet.
As a workaround I would suggest, that you create a new layout file with your RecyclerView only: vertical_recycler_view.xml

<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent" />

Now you can inflate and add the RecyclerView with scrollbars everywhere you want: MyCustomViewGroup.java

public class MyCustomViewGroup extends FrameLayout
{
    public MyCustomViewGroup(Context context)
    {
        super(context);

        RecyclerView verticalRecyclerView = (RecyclerView) LayoutInflater.from(context).inflate(R.layout.vertical_recycler_view, null);
        verticalRecyclerView.setLayoutManager(new LinearLayoutManager(context, LinearLayoutManager.VERTICAL, false));
        addView(verticalRecyclerView);
    }
}

I would prefer to use ContextThemeWrapper for that, because it can be used dynamically from code.

First define in Style.xml:

<style name="ScrollbarRecyclerView" parent="android:Widget">
    <item name="android:scrollbars">vertical</item>
</style>

And then whenever you initialize your RecyclerView use ContextThemeWrapper:

RecyclerView recyclerView = new RecyclerView(new ContextThemeWrapper(context, R.style.ScrollbarRecyclerView));

Just in xml properties

<android.support.v7.widget.RecyclerView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/recyclerView"
    android:scrollbars="vertical" <!-- type of scrollbar -->
    android:scrollbarThumbVertical="@android:color/darker_gray"  <!--color of scroll bar-->
    android:scrollbarSize="5dp"> <!--width of scroll bar-->

</android.support.v7.widget.RecyclerView>