Android Development for Beginners : Starter Gist for XML

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.android.practiceset2.MainActivity">

    <TextView
        android:id="@+id/display_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="45sp" />

    <TextView
        android:id="@+id/display_text_view_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="45sp" />

    <TextView
        android:id="@+id/display_text_view_3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="45sp" />

</LinearLayout>

In activity_main.xml file

Replace this: tools:context="com.example.android.practiceset2.MainActivity">

To this: tools:context="com.example.practiceset2.MainActivity">

and in MainActivity.java file

This is the Final Working code for me. 
I'm using Windows 10 (64 bit), and android studio 4.2 (beta 4).

_I tried the solution by @fedor90 and then the following code:_

### **for "activity_main.xml":**

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.example.practiseset2.MainActivity">">

    <TextView
        android:id="@+id/display_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="45sp" />

    <TextView
        android:id="@+id/display_text_view_2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="45sp" />

    <TextView
        android:id="@+id/display_text_view_3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:textSize="45sp" />

</LinearLayout>


**### for "MainActivity.java "**


package com.example.practiseset2;

import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import android.widget.TextView;

import com.example.practiseset2.R;

public class MainActivity extends AppCompatActivity {

        @Override
        protected void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);
                // PASTE CODE YOU WANT TO TEST HERE

        }

        /**
         * Display methods that allow the text to appear on the screen. Don't worry if you don't know
         * how these work yet. We'll be covering them in lesson 3.
         */

        public void display(String text) {
                TextView t = (TextView) findViewById(R.id.display_text_view);
                t.setText(text);
        }

        public void display(int text) {
                TextView t = (TextView) findViewById(R.id.display_text_view);
                t.setText(text + "");
        }

        public void display1(String text) {
                display(text);
        }

        public void display2(String text) {
                TextView t = (TextView) findViewById(R.id.display_text_view_2);
                t.setText(text);
        }

        public void display3(String text) {
                TextView t = (TextView) findViewById(R.id.display_text_view_3);
                t.setText(text);
        }
}
``

for those who are facing a issue with unable to resolve display_text_view issue just check your text view id because in my id "+" was not present

Thank you!