Free Response Questions

Section 5.9 Free Response Questions

Section 5.9.1 Free Response - Trio A

The following is a free response question from 2014. It was question 4 on the exam. You can see all the free response questions from past exams at https://apstudents.collegeboard.org/courses/ap-computer-science-a/free-response-questions-by-year

https://apstudents.collegeboard.org/courses/ap-computer-science-a/free-response-questions-by-year

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Question 4. The menu at a lunch counter includes a variety of sandwiches, salads, and drinks. The menu also allows a customer to create a “trio,” which consists of three menu items: a sandwich, a salad, and a drink. The price of the trio is the sum of the two highest-priced menu items in the trio; one item with the lowest price is free. Each menu item has a name and a price. The four types of menu items are represented by the four classes Sandwich, Salad, Drink, and Trio. All four classes implement the following MenuItem interface.

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Interfaces are no longer on the AP CSA exam, but you can just treat an interface like a superclass. Just substitute the word class instead of interface below and your TrioClass can extend MenuItem instead of implementing the interface.

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public interface MenuItem
{
    /**
     * @return the name of the menu item
     */
    String getName();

    /**
     * @return the price of the menu item
     */
    double getPrice();
}

The following diagram shows the relationship between the MenuItem interface and the Sandwich, Salad, Drink, and Trio classes.

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Figure 5.9.1. UML class diagram showing MenuItem is implemented by Sandwich, Salad, Drink, and Trio.
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For example, assume that the menu includes the following items. The objects listed under each heading are instances of the class indicated by the heading.

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The menu allows customers to create Trio menu items, each of which includes a sandwich, a salad, and a drink. The name of the Trio consists of the names of the sandwich, salad, and drink, in that order, each separated by “/” and followed by a space and then “Trio”. The price of the Trio is the sum of the two highest-priced items in the Trio; one item with the lowest price is free. A trio consisting of a cheeseburger, spinach salad, and an orange soda would have the name

"Cheeseburger/Spinach
      Salad/Orange Soda Trio"

and a price of $4.00 (the two highest prices are $2.75 and $1.25). Similarly, a trio consisting of a club sandwich, coleslaw, and a cappuccino would have the name

"Club
      Sandwich/Coleslaw/Cappuccino Trio"

and a price of $6.25 (the two highest prices are $2.75 and $3.50).

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Subsection 5.9.1.1 Try and Solve It

Activity 5.9.1.

Write the Trio class (near the end of the code below) that implements the MenuItem interface (which is like extending a class). Your implementation must include a constructor that takes three parameters representing a sandwich, salad, and drink. The main method has code to test the result.

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import java.text.*;

interface MenuItem
{
    /**
     * @return the name of the menu item
     */
    String getName();

/**
     * @return the price of the menu item
     */
    double getPrice();
}

class SimpleLunchItem implements MenuItem
{
    private String name;
    private double price;

public SimpleLunchItem(String aName, double aPrice)
    {
        name = aName;
        price = aPrice;
    }

public String getName()
    {
        return name;
    }

public double getPrice()
    {
        return price;
    }

public String toString()
    {
        DecimalFormat money = new DecimalFormat("0.00");
        return getName() + " " + money.format(getPrice());
    }
}

class Drink extends SimpleLunchItem
{
    public Drink(String name, double price)
    {
        super(name, price);
    }
}

class Salad extends SimpleLunchItem
{
    public Salad(String name, double price)
    {
        super(name, price);
    }
}

class Sandwich extends SimpleLunchItem
{
    public Sandwich(String name, double price)
    {
        super(name, price);
    }
}

// Declare the Trio class.  It must implement the MenuItem interface.
public class Trio implements MenuItem
{
    // declare the instance variables that you need for a trio object

// write a constructor that takes a Sandwich, Salad, and a Drink, in that order

// write the getName method it should return
    // sandwich name/salad name/drink name Trio

// write the getPrice method
    // it should return the price of the two highest price items in the trio.

public static void main(String[] args)
    {
        Sandwich burger = new Sandwich("Cheeseburger", 2.75);
        Sandwich club = new Sandwich("Club Sandwich", 2.75);
        Salad spinachSalad = new Salad("Spinach Salad", 1.25);
        Salad coleslaw = new Salad("Coleslaw", 1.25);
        Drink orange = new Drink("Orange Soda", 1.25);
        Drink cap = new Drink("Cappuccino", 3.50);
        Trio trio1 = new Trio(burger, spinachSalad, orange);
        System.out.println(
                "It should print Cheeseburger/Spinach Salad/Orange Soda Trio and"
                    + " it prints: "
                        + trio1.getName());
        System.out.println(
                "It should print 4.0 and it prints: " + trio1.getPrice());
        Trio trio2 = new Trio(club, coleslaw, cap);
        System.out.println(
                "It should print Club Sandwich/Coleslaw/Capuccino Trio and it"
                    + " prints: "
                        + trio2.getName());
        System.out.println(
                "It should print 6.25 and it prints: " + trio2.getPrice());
    }
}
====
import static org.junit.Assert.*;

import org.junit.*;

import java.io.*;

public class RunestoneTests extends CodeTestHelper
{
    public RunestoneTests()
    {
        super("Trio");
    }

@Test
    public void test1()
    {
        String output = getMethodOutput("main");
        String expect =
                "It should print Cheeseburger/Spinach Salad/Orange Soda Trio and it prints:"
                    + " Cheeseburger/Spinach Salad/Orange Soda Trio\n"
                    + "It should print 4.0 and it prints: 4.0\n"
                    + "It should print Club Sandwich/Coleslaw/Capuccino Trio and it prints: Club"
                    + " Sandwi\n"
                    + "ch/Coleslaw/Cappuccino Trio\n"
                    + "It should print 6.25 and it prints: 6.25";

boolean passed = removeSpaces(expect).equals(removeSpaces(output));

getResults(expect, output, "Running main", passed);
        assertTrue(passed);
    }

@Test
    public void test2()
    {
        String target = "implements MenuItem";

boolean passed = checkCodeContains(target);
        assertTrue(passed);
    }

@Test
    public void test3()
    {
        String output = checkConstructor("Sandwich, Salad, Drink");
        String expect = "pass";

boolean passed =
                getResults(
                        expect,
                        output,
                        "Checking Trio constructor with 3 arguments: Sandwich, Salad, Drink");
        assertTrue(passed);
    }

@Test
    public void test4()
    {
        String target = "public String getName()";

boolean passed = checkCodeContains("getName()", target);
        assertTrue(passed);
    }

@Test
    public void test5()
    {
        String target = "public double getPrice()";

boolean passed = checkCodeContains("getPrice()", target);
        assertTrue(passed);
    }

@Test
    public void test6()
    {
        Sandwich burger = new Sandwich("Hamburger", 7.50);
        Salad coleslaw = new Salad("Coleslaw", 2);
        Drink orange = new Drink("Orange Soda", 1.25);
        Trio trio1 = new Trio(burger, coleslaw, orange);

String name = trio1.getName();
        String expect = "Hamburger/Coleslaw/Orange Soda Trio";

boolean passed = getResults(expect, name, "Checking getName()");
        assertTrue(passed);
    }

@Test
    public void test7()
    {
        Sandwich burger = new Sandwich("Hamburger", 7.50);
        Salad coleslaw = new Salad("Coleslaw", 2);
        Drink orange = new Drink("Orange Soda", 1.25);
        Trio trio1 = new Trio(burger, coleslaw, orange);

String name = "" + trio1.getPrice();
        String expect = "9.5";

boolean passed = getResults(expect, name, "Checking getPrice()");
        assertTrue(passed);
    }
}

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Section 5.9.2 Trio Student Solution 1

https://apstudents.collegeboard.org/courses/ap-computer-science-a/free-response-questions-by-year

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public interface MenuItem
{
    /**
     * @return the name of the menu item
     */
    String getName();

    /**
     * @return the price of the menu item
     */
    double getPrice();
}

The following diagram shows the relationship between the MenuItem interface and the Sandwich, Salad, Drink, and Trio classes.

🔗

For example, assume that the menu includes the following items. The objects listed under each heading are instances of the class indicated by the heading.

🔗

"Cheeseburger/Spinach
      Salad/Orange Soda Trio"

and a price of $4.00 (the two highest prices are $2.75 and $1.25). Similarly, a trio consisting of a club sandwich, coleslaw, and a cappuccino would have the name

"Club
      Sandwich/Coleslaw/Cappuccino Trio"

and a price of $6.25 (the two highest prices are $2.75 and $3.50).

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Subsection 5.9.2.1 Grading Rubric

Below is the grading rubric for the Trio class problem.

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Figure 5.9.3. The grading rubric for the Trio class problem.
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Subsection 5.9.2.2 Practice Grading

The following is the first sample student response.

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Figure 5.9.4. The first sample student response to the Trio class problem.
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Apply the grading rubric shown above as you answer the following questions.

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Apply the Grading Rubric

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Activity 5.9.1.

Should the student earn 1 point for the correct declaration of the Trio class?

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Yes
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This declares the class correctly as public class Trio implements MenuItem
No
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What do you think is wrong with the class declaration?

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Activity 5.9.2.

Should the student earn 1 point for declaring the private instance variables (sandwich, salad, and drink or name and price)?

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Yes
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All instance variables are declared private (sand, sal, and dri) and are of the appropriate type (Sandwich, Salad, and Drink)
No
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What do you think is wrong with the instance variables declaration?

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Activity 5.9.3.

Should the student earn 1 point for declaring the constructor correctly?

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Yes
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This solution declares the constructor as public Trio(Sandwich a, Salad b, Drink c)
No
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What do you think is wrong with the constructor declaration?

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Activity 5.9.4.

Should the student earn 1 point for correctly initializing the appropriate instance variables in the constructor?

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Yes
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This solution initializes the private instance variables (sand, sal, and dri) correctly with the values from the parameters (a,b, and c).
No
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What do you think is wrong with the initialization of the instance variables in the constructor?

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Activity 5.9.5.

Should the student earn 1 point for correctly declaring the methods in the MenuItem interface (getName and getPrice)?

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Yes
🔗
This solution contains correct declarations for public String getName() and public double getPrice().
No
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To implement an interface the class must have a getName and getPrice method as defined by the MenuItem interface.

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Activity 5.9.6.

Should the student earn 1 point for correctly constructing the string to return from getName and making it available to be returned?

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Yes
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This solution doesn’t include the "Trio" at the end of the name so it loses this point.
No
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While the name is mostly correct, it is missing the word "Trio" at the end which means it loses this point.

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Activity 5.9.7.

Should the student earn 1 point for returning a constructed string from getName?

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Yes
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This solution does return the constructed string.
No
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Even though the string is not correct it was constructed and returned.

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Activity 5.9.8.

Should the student earn 1 point for correctly calculating the price and making it available to be returned from getPrice?

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Yes
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This solution does compute the price correctly.
No
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There are only 3 possibilities for which is the cheapest item and this correctly deals with the 3 cases.

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Activity 5.9.9.

Should the student earn 1 point for returning the calculated price in getPrice?

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Yes
🔗
This solution does return the calculated price.
No
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What do you think is wrong with the return statement?

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Activity 5.9.10.

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Section 5.9.3 Trio Student Solution 2

https://apstudents.collegeboard.org/courses/ap-computer-science-a/free-response-questions-by-year

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public interface MenuItem
{
    /**
     * @return the name of the menu item
     */
    String getName();

    /**
     * @return the price of the menu item
     */
    double getPrice();
}

The following diagram shows the relationship between the MenuItem interface and the Sandwich, Salad, Drink, and Trio classes.

🔗

For example, assume that the menu includes the following items. The objects listed under each heading are instances of the class indicated by the heading.

🔗

"Cheeseburger/Spinach
      Salad/Orange Soda Trio"

and a price of $4.00 (the two highest prices are $2.75 and $1.25). Similarly, a trio consisting of a club sandwich, coleslaw, and a cappuccino would have the name

"Club
      Sandwich/Coleslaw/Cappuccino Trio"

and a price of $6.25 (the two highest prices are $2.75 and $3.50).

🔗

Subsection 5.9.3.1 Grading Rubric

Below is the grading rubric for the Trio class problem.

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Subsection 5.9.3.2 Practice Grading

The following is the second sample student response.

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Figure 5.9.4. The start of the second sample student response to the Trio class problem.
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Figure 5.9.5. The end of the second sample student response to the Trio class problem.
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Apply the grading rubric shown above as you answer the following questions.

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Apply the Grading Rubric

🔗

Activity 5.9.1.

Should the student earn 1 point for the correct declaration of the Trio class?

🔗

Yes
🔗
This declares the class correctly as public class Trio implements MenuItem
No
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What do you think is wrong with the class declaration?

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Activity 5.9.2.

Should the student earn 1 point for declaring the private instance variables (sandwich, salad, and drink or name and price)?

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Yes
🔗
Remember that all instance variables should be declared private so that the class controls access to the variables.
No
🔗
The student did not make the instance variables private, so the student does not get this point.

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Activity 5.9.3.

Should the student earn 1 point for declaring the constructor correctly?

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Yes
🔗
This solution declares the constructor as public Trio(Sandwich s, Salad sa, Drink d)
No
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What do you think is wrong with the constructor declaration?

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Activity 5.9.4.

Should the student earn 1 point for correctly initializing the appropriate instance variables in the constructor?

🔗

Yes
🔗
This solution initializes the instance variables (sandwich, salad, and drink) correctly with the values from the parameters (s, sa, and d).
No
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What do you think is wrong with the initialization of the instance variables in the constructor?

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Activity 5.9.5.

Should the student earn 1 point for correctly declaring the methods in the MenuItem interface (getName and getPrice)?

🔗

Yes
🔗
This solution contains correct declarations for public String getName() and public double getPrice().
No
🔗
To implement an interface the class must have a getName and getPrice method as defined by the MenuItem interface.

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Activity 5.9.6.

Should the student earn 1 point for correctly constructing the string to return from getName and making it available to be returned?

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Yes
🔗
Look at what getName is supposed to return.
No
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This solution doesn’t include the "/" between the sandwich and salad and between the salad and the drink and is also missing the "Trio" at the end of the name, so it loses this point.

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Activity 5.9.7.

Should the student earn 1 point for returning a constructed string from getName?

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Yes
🔗
This solution does return the constructed string, even if the string is not completely correct.
No
🔗
Even though the string is not correct it was constructed and returned.

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Activity 5.9.8.

Should the student earn 1 point for correctly calculating the price and making it available to be returned from getPrice?

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Yes
🔗
What if b is equal to c but both are greater than a?
No
🔗
This does not always compute the price correctly (when b is equal to c and they are both greater than a, it should return b+c, not a+b).

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Activity 5.9.9.

Should the student earn 1 point for returning the calculated price in getPrice?

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Yes
🔗
This solution does return the calculated price, even if that price is not always correct.
No
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This point is earned if the student attempted to calculate the price and returned what was calculated.

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Activity 5.9.10.

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Section 5.9.4 Trio Student Solution 3

https://apstudents.collegeboard.org/courses/ap-computer-science-a/free-response-questions-by-year

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public interface MenuItem
{
    /**
     * @return the name of the menu item
     */
    String getName();

    /**
     * @return the price of the menu item
     */
    double getPrice();
}

The following diagram shows the relationship between the MenuItem interface and the Sandwich, Salad, Drink, and Trio classes.

🔗

For example, assume that the menu includes the following items. The objects listed under each heading are instances of the class indicated by the heading.

🔗

"Cheeseburger/Spinach
      Salad/Orange Soda Trio"

and a price of $4.00 (the two highest prices are $2.75 and $1.25). Similarly, a trio consisting of a club sandwich, coleslaw, and a cappuccino would have the name

"Club
      Sandwich/Coleslaw/Cappuccino Trio"

and a price of $6.25 (the two highest prices are $2.75 and $3.50).

🔗

Subsection 5.9.4.1 Grading Rubric

Below is the grading rubric for the Trio class problem.

🔗

Subsection 5.9.4.2 Practice Grading

The following is the third sample student response.

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Apply the grading rubric shown above as you answer the following questions.

🔗

Apply the Grading Rubric

🔗

Activity 5.9.1.

Should the student earn 1 point for the correct declaration of the Trio class?

🔗

Yes
🔗
This declares the class correctly as public class Trio implements MenuItem
No
🔗
What do you think is wrong with the class declaration?

🔗

Activity 5.9.2.

Should the student earn 1 point for declaring the private instance variables (sandwich, salad, and drink or name and price)?

🔗

Yes
🔗
Do you see any instance variables declared here?
No
🔗
The student did not declare any instance variables.

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Activity 5.9.3.

Should the student earn 1 point for declaring the constructor correctly?

🔗

Yes
🔗
This solution declares the constructor as public Trio(Sandwich sandwich, Salad salad, Drink drink)
No
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What do you think is wrong with the constructor declaration?

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Activity 5.9.4.

Should the student earn 1 point for correctly initializing the appropriate instance variables in the constructor?

🔗

Yes
🔗
This solution doesn’t have any instance variables declared and doesn’t try to use the parameter values.
No
🔗
There is no attempt to set the instance variables (which haven’t been declared) to the parameter values.

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Activity 5.9.5.

Should the student earn 1 point for correctly declaring the methods in the MenuItem interface (getName and getPrice)?

🔗

Yes
🔗
To implement an interface the class must have both a getName and getPrice method.
No
🔗
This class is missing both the interface methods.

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Activity 5.9.6.

Should the student earn 1 point for correctly constructing the string to return from getName and making it available to be returned?

🔗

Yes
🔗
While the toString method exists and correctly creates the name string, it is not called by a getName method.
No
🔗
Since there is no getName method this point can not be awarded.

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Activity 5.9.7.

Should the student earn 1 point for returning a constructed string from getName?

🔗

Yes
🔗
While the toString method exists and correctly creates and returns the name string, it is not called by a getName method.
No
🔗
Since there is no getName method this point can not be awarded.

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Activity 5.9.8.

Should the student earn 1 point for correctly calculating the price and making it available to be returned from getPrice?

🔗

Yes
🔗
While there is a method that calculates the price correctly, it is the wrong method.
No
🔗
There is no getPrice method so the student can not earn this point.

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Activity 5.9.9.

Should the student earn 1 point for returning the calculated price in getPrice?

🔗

Yes
🔗
While there is a method that calculates the price correctly and returns it, it is the wrong method.
No
🔗
There is no getPrice method so the student can not earn this point.

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Activity 5.9.10.

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You have attempted of activities on this page.

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