New method in MainActivity.java

/**
 * This method displays the given text on the screen.
 */
private void displayMessage(String message) {
    TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
    priceTextView.setText(message);
}

New method in MainActivity.java

/**
 * This method displays the given price on the screen.
 */
private void displayPrice(int number) {
       TextView priceTextView = (TextView) findViewById(R.id.price_text_view);
       priceTextView.setText(NumberFormat.getCurrencyInstance().format(number));
}