// This is the definition of a class named MainActivity. Although the class has many

// methods, we show the definition of only one of them.

public class MainActivity extends AppCompatActivity {


    // The “void” in the signature (first line) of the definition of this method

    // indicates that the method does not produce a return value.

    private void displayQuantity(int number) {

        TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);

        quantityTextView.setText("" + number);