Java While Loop for ArrayList Won't Terminate

I'm trying to design a shopping cart that reads dollar amounts and then prints those values back. My while loop, however, won't terminate and my arraylist is storing erroneous values.

 /**
 * This method is the shopping cart
 */
public static void shoppingCart()
{
    // create scanner objects
    Scanner textReader = new Scanner(System.in);
    Scanner numberReader = new Scanner(System.in);
    // declare variables
    int counter = 0;
    // create arraylist object
    ArrayList<Double> cartItems = new ArrayList<Double>();
    // create decimal format object
    DecimalFormat dollarformatter = new DecimalFormat("$#0.00");
    // print out the first prompt
    System.out.print("Would you like to input item/s - y/n: ");
    String response = textReader.nextLine();
    System.out.println();
    // create while loop to restrict responses to single characters
    while ((!response.equalsIgnoreCase("y")) && (!response.equalsIgnoreCase("n")))
    {
        System.out.print("Sorry - we need a y/n: ");
        response = textReader.nextLine();
        System.out.println();
    }
    // create while loop for positive response
    while ((response.equalsIgnoreCase("y")))
    {
        System.out.print("Please enter an item price, or -1 to exit: $");
        double values = numberReader.nextDouble();
        cartItems.add(values);
        if ((values > (-1)))
        {
            System.out.print("Please enter another item price, or -1 to exit: $");
            values = numberReader.nextDouble();
            cartItems.add(values);
        }
        else if ((values <= (-1)))
        {
            System.out.println();
            System.out.println("********** Here are your items **********");
            System.out.println();
            for (counter = 0; counter < cartItems.size(); counter++)
            {
                System.out.println("Item #" + (counter + 1) + ": " + cartItems.get(counter));
            }
        }
    }
    System.out.println();
    System.out.println("********** Thank you for using the shopping cart **********");
}

The results should look like this:

But this is my output:

• The while loop won't terminate and goes back to the first prompt: "please enter an item price, or -1 to exit:"
• The program keeps counting the "-1" as part of the arraylist. The "-1" value is supposed to act as a "no" and terminate the addition of more elements to the arrayList but in my code, it gets absorbed into the arrayList. I've tried turning the "-1" into a string to get the program to "ignore" it but it doesn't work.
• After the program lists the final item (in my output it is #3), it is supposed to ask if the user wants to delete an item. I have not gotten this far as I am quite stumped as to why my while loop refuses to terminate and why "-1" keeps getting included in my arraylist. Any help with this is greatly appreciated it as I've been mulling over this for a day now with no luck.