This is an Android Basics Nanodegree Program Practice Set. Lesson 4. Making an App interactive. I read many comments how confusing to set up a new project before even start the practice part. I got it. A few updates came out since and the first step for beginners can be hard. So, here is my "create a new project" first step.

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="android.example.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>

MainActivity.java

package android.example.practiceset2;

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

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
        int raspberryPrice = 5;
        display1("1 box: $" + raspberryPrice);
        raspberryPrice = 10;
        display2("2 boxes: $" + (raspberryPrice));
        display3("3 boxes: $" + (raspberryPrice * 3));
    }

    /**
     * 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);
    }
}

Heya, thanks a million. Will try it out, if I don't get it right will write again.

That's fine :)
I hope it works and you will have more questions.

A little note for everyone who is coming from the discussion:
Please, keep an eye:

• on package name(first line),
• the imports name,
• TextView id's field in the XML file.