This is my Pasteboard place, where small chunk of Code stays until use it.

MainActivity.java

/**
 * IMPORTANT: Add your package below. Package name can be found in the project's AndroidManifest.xml file.
 * This is the package name our example uses:
 * 
 * package com.example.android.justjava; 
 * 
 */


import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.TextView;

/**
 * This app displays an order form to order coffee.
 */
public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    /**
     * This method is called when the order button is clicked.
     */
    public void submitOrder(View view) {
        display(1);
    }

    /**
     * This method displays the given quantity value on the screen.
     */
    private void display(int number) {
        TextView quantityTextView = (TextView) findViewById(R.id.quantity_text_view);
        quantityTextView.setText("" + number);
    }
    
   /**
    * 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));
}
}

Udacity lesson for Android basics, this is the Java code for the Main activity from Android studio.