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Section 4.39 Unit 4B - Free Response - CookieOrder A

The following is a free response question from 2010. It was question 1 on the exam. You can see all the free response questions from past exams at Past AP CSA Exams.
Question 1. An organization raises money by selling boxes of cookies. A cookie order specifies the variety of cookie and the number of boxes ordered. The declaration of the CookieOrder class is shown below. 
public class CookieOrder
{
    /** Constructs a new CookieOrder object */
    public CookieOrder(String variety, int numBoxes)
    {
        /* implementation not shown */
    }

    /**
     * @return the variety of cookie being ordered
     */
    public String getVariety()
    {
        /* implementation not shown */
    }

    /**
     * @return the number of boxes being ordered
     */
    public int getNumBoxes()
    {
        /* implementation not shown */
    }

    // There may be instance variables, constructors, and methods that are not
    // shown.
}
The MasterOrder class maintains a list of the cookies to be purchased. The declaration of the MasterOrder class is shown below. 
public class MasterOrder
{
    /** The list of all cookie orders */
    private List<CookieOrder> orders;

    /** Constructs a new MasterOrder object */
    public MasterOrder()
    {
        orders = new ArrayList<CookieOrder>();
    }

    /**
     * Adds theOrder to the master order.
     *
     * @param theOrder the cookie order to add to the master order
     */
    public void addOrder(CookieOrder theOrder)
    {
        orders.add(theOrder);
    }

    /**
     * @return the sum of the number of boxes of all of the cookie orders
     */
    public int getTotalBoxes()
    {
        /* to be implemented in part (a) */
    }

    // There may be instance variables, constructors, and methods that are not
    // shown.
}
Part a. The getTotalBoxes method computes and returns the sum of the number of boxes of all cookie orders. If there are no cookie orders in the master order, the method returns 0.

Subsection 4.39.1 How to Solve This

These multiple choice questions may help you write your solution.

Activity 4.39.1.

What type of loop is best for this problem?
  • while
  • While loops are better for problems where you are looping until a condition is true or false.
  • for
  • This will work, but it is more concise to use a for-each loop.
  • for-each
  • Correct! This is the most concise way to access every CookieOrder.

Activity 4.39.2.

What will you return at the end of this method?
  • The total number of cookie orders
  • The number of cookie orders is the length of the orders List. We are going one step farther in counting boxes. Try again!
  • The total number of cookie boxes
  • Correct!
  • The total number of cookies
  • We don’t know how many cookies are in each box. Try again!

Activity 4.39.3.

What is wrong with this code? 
public int getTotalBoxes()
{
    for (CookieOrder co : this.orders)
    {
      int sum = sum + co.getNumBoxes();
    }
    return sum;
}
  • It does not count the total number of boxes because the sum variable’s scope is only inside the loop.
  • Correct! int sum must be initialized before the loop.
  • It counts orders, not boxes
  • co.getNumBoxes returns the number of boxes for a CookieOrder.
  • Nothing.
  • Take a closer look inside the loop.

Subsection 4.39.2 Mixed Up Code

Activity 4.39.4.

The method getTotalBoxes below contains the correct code for one solution to this problem, but it is mixed up. Drag the needed code from the left to the right and put them in order with the correct indention so that the code would work correctly.

Subsection 4.39.3 Solve Part A

Activity 4.39.5.

FRQ Cookie Order Part A: Complete the method getTotalBoxes below.
You have attempted of activities on this page.
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