ArrayList.java

ArrayList<String> words = new ArrayList<String>();
        words.add("One");

  //Find the rootView of Numbers activity
        LinearLayout rootView = findViewById(R.id.rootView);
        //Create a TextView programmatically
        TextView wordView = new TextView(this);
        //Show first element of the ArrayList ib that TextView
        wordView.setText(words.get(0));
        //Attach TextView with the rootView
        rootView.addView(wordView);

Numers.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/rootView"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context=".NumbersActivity">

</LinearLayout>