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 Past AP CSA Exams.

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.

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.

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.

Figure 5.9.1. UML class diagram showing MenuItem is implemented by Sandwich, Salad, Drink, and Trio.

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.

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).

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.

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);
    }
}

Section 5.9.2 Trio Student Solution 1

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 Past AP CSA Exams.

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.

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.

Figure 5.9.3. UML class diagram showing MenuItem is implemented by Sandwich, Salad, Drink, and Trio.

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.

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).

Subsection 5.9.2.1 Grading Rubric

Below is the grading rubric for the Trio class problem.

Figure 5.9.5. The grading rubric for the Trio class problem.

Subsection 5.9.2.2 Practice Grading

The following is the first sample student response.

Figure 5.9.6. The first sample student response to the Trio class problem.

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

Apply the Grading Rubric

Activity 5.9.2.

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 5.9.3.

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

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

Activity 5.9.4.

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

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

Activity 5.9.5.

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

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

Activity 5.9.6.

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.

Activity 5.9.7.

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

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

Activity 5.9.8.

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

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

Activity 5.9.9.

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

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

Activity 5.9.10.

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

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

Activity 5.9.11.

Section 5.9.3 Trio Student Solution 2

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 Past AP CSA Exams.

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.

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.

Figure 5.9.7. UML class diagram showing MenuItem is implemented by Sandwich, Salad, Drink, and Trio.

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.

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).

Subsection 5.9.3.1 Grading Rubric

Below is the grading rubric for the Trio class problem.

Figure 5.9.9. The grading rubric for the Trio class problem.

Subsection 5.9.3.2 Practice Grading

The following is the second sample student response.

Figure 5.9.10. The start of the second sample student response to the Trio class problem.

Figure 5.9.11. The end of the second sample student response to the Trio class problem.

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

Apply the Grading Rubric

Activity 5.9.12.

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 5.9.13.

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

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.

Activity 5.9.14.

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

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

Activity 5.9.15.

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
What do you think is wrong with the initialization of the instance variables in the constructor?

Activity 5.9.16.

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.

Activity 5.9.17.

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

Yes
Look at what getName is supposed to return.
No
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.

Activity 5.9.18.

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

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.

Activity 5.9.19.

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

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).

Activity 5.9.20.

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

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

Activity 5.9.21.

Section 5.9.4 Trio Student Solution 3

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 Past AP CSA Exams.

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.

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.

Figure 5.9.12. UML class diagram showing MenuItem is implemented by Sandwich, Salad, Drink, and Trio.

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.

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).

Subsection 5.9.4.1 Grading Rubric

Below is the grading rubric for the Trio class problem.

Figure 5.9.14. The grading rubric for the Trio class problem.

Subsection 5.9.4.2 Practice Grading

The following is the third sample student response.

Figure 5.9.15. The start of the second sample student response to the Trio class problem.

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

Apply the Grading Rubric

Activity 5.9.22.

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 5.9.23.

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.

Activity 5.9.24.

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
What do you think is wrong with the constructor declaration?

Activity 5.9.25.

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.

Activity 5.9.26.

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.

Activity 5.9.27.

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.

Activity 5.9.28.

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.

Activity 5.9.29.

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.

Activity 5.9.30.

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.

Activity 5.9.31.

Section 5.9.5 Retired FRQ - Inheritance - NumberGroup - Part B

Part b. A range represents a number group that contains all (and only) the integers between a minimum value and a maximum value, inclusive. Write the Range class, which is a NumberGroup. The Range class represents the group of int values that range from a given minimum value up through a given maximum value, inclusive. For example, the declaration NumberGroup range1 = new Range(-3, 2); represents the group of integer values -3, -2, -1, 0, 1, 2.

Write the complete Range class. Include all necessary instance variables and methods as well as a constructor that takes two int parameters. The first parameter represents the minimum value, and the second parameter represents the maximum value of the range. You may assume that the minimum is less than or equal to the maximum. Write the contains method which returns true or false if a given int argument is within the range set up by the constructor.

Subsection 5.9.5.1 Try and Solve It

Activity 5.9.32.

Complete the class Range below with instance variables, a constructor, and a contains method.

class NumberGroup
{
    /* Implementation not shown */
}

public class Range extends NumberGroup
{
    // Write the instance variables for the Range class here

// Write the Range constructor with 2 parameters
    // for the minimum and maximum values in the range

// Write the contains method which tests whether a
    // given number is in the range.

// Main method to test the class
    public static void main(String[] args)
    {
        System.out.println("This is testing the constructor");
        Range test = new Range(5, 8);
        // Test the contains method
        System.out.println(
                "Does the range contain 4 (should be false): " + test.contains(4));
        System.out.println(
                "Does the range contain 5 (should be true): " + test.contains(5));
    } // end of main
} // end of class
====
import static org.junit.Assert.*;

import org.junit.*;

import java.io.*;

// import java.util.ArrayList;

public class RunestoneTests extends CodeTestHelper
{
    public RunestoneTests()
    {
        super("Range");
        // CodeTestHelper.sort = true;
    }

@Test
    public void testMain1()
    {
        boolean passed = false;

String expect =
                "This is testing the constructor\n"
                    + "Does the range contain 4 (should be false): false\n"
                    + "Does the range contain 5 (should be true): true";

String output = getMethodOutput("main");

passed = getResults(expect, output, "Checking for expected output from main");
        assertTrue(passed);
    }

@Test
    public void testMain2()
    {
        boolean passed = false;

Range test = new Range(5, 80);
        // Test the contains method
        String expect = "false";
        String output = "" + test.contains(0);

passed = getResults(expect, output, "Checking that Range(5, 80) contains(0)");
        assertTrue(passed);
    }

@Test
    public void testMain3()
    {
        boolean passed = false;

Range test = new Range(5, 80);
        // Test the contains method
        String expect = "true";
        String output = "" + test.contains(10);

passed = getResults(expect, output, "Checking that Range(5, 80) contains(10)");
        assertTrue(passed);
    }
}

Section 5.9.6 Retired FRQ - Inheritance - NumberGroup - Part C

Part c. The MultipleGroups class represents a collection of NumberGroup objects and is a NumberGroup. The MultipleGroups class stores the number groups in the instance variable groupList (shown below), which is initialized in the constructor.

private ArrayList<NumberGroup> groupList;

Write the MultipleGroups method contains. The method takes an integer and returns true if and only if the integer is contained in one or more of the number groups in groupList.

For example, suppose multiple1 has been declared as an instance of MultipleGroups and consists of the three ranges created by the calls:

new Range(5, 8)
new Range(10, 12)
new Range(1, 6)

The following table shows the results of several calls to contains.

Subsection 5.9.6.1 Try and Solve It

Write the method contains below in the class MultiGroups. (Note that the original AP Question involved a NumberGroup interface which has been replaced with inheritance here).

Activity 5.9.33.

Write the method contains below in the class MultiGroups.

import java.util.ArrayList;

class NumberGroup
{
    public boolean contains(int num)
    {
        /* Implementation not shown */
        return true;
    }
}

class Range extends NumberGroup
{
    // copy in your Range class from the previous lesson here
}

public class MultiGroups extends NumberGroup
{

private ArrayList<NumberGroup> groupList;

public MultiGroups(Range r1, Range r2, Range r3)
    {
        groupList = new ArrayList<NumberGroup>();
        groupList.add(r1);
        groupList.add(r2);
        groupList.add(r3);
    }

/**
     * Returns true if at least one of the number groups in this multiple group
     * contains num; false otherwise
     */
    public boolean contains(int num)
    {
        // Write the MultiGroup contains method here

}

// Main method to test the class
    public static void main(String[] args)
    {
        MultiGroups multiple1 =
                new MultiGroups(
                        new Range(5, 8), new Range(10, 12), new Range(1, 6));
        System.out.println(
                "Multiple1 contains 2 (should be true)? " + multiple1.contains(2));
        System.out.println(
                "Multiple1 contains 9 (should be false)? "
                        + multiple1.contains(9));
        System.out.println(
                "Multiple1 contains 6 (should be true)? " + multiple1.contains(6));
    } // end of main
}
====
import static org.junit.Assert.*;

import org.junit.*;

import java.io.*;

// import java.util.ArrayList;

public class RunestoneTests extends CodeTestHelper
{
    public RunestoneTests()
    {
        super("MultiGroups");
        // CodeTestHelper.sort = true;
    }

@Test
    public void testMain1()
    {
        boolean passed = false;

String expect =
                "Multiple1 contains 2 (should be true)? true\n"
                    + "Multiple1 contains 9 (should be false)? false\n"
                    + "Multiple1 contains 6 (should be true)? true";

String output = getMethodOutput("main");

passed = getResults(expect, output, "Checking for expected output from main");
        assertTrue(passed);
    }

@Test
    public void testMain2()
    {
        boolean passed = false;

MultiGroups multiple1 =
                new MultiGroups(new Range(5, 8), new Range(10, 12), new Range(15, 20));

String expect = "false";
        String output = "" + multiple1.contains(0);

passed =
                getResults(
                        expect,
                        output,
                        "Checking that MultiGroups with Range(5, 8), Range(10, 12), Range(15, 20)"
                            + " contains(0) should be false");
        assertTrue(passed);
    }

@Test
    public void testMain3()
    {
        boolean passed = false;

MultiGroups multiple1 =
                new MultiGroups(new Range(5, 8), new Range(10, 12), new Range(15, 20));

String expect = "true";
        String output = "" + multiple1.contains(11);

passed =
                getResults(
                        expect,
                        output,
                        "Checking that MultiGroups with Range(5, 8), Range(10, 12), Range(15, 20)"
                            + " contains(11) should be true");
        assertTrue(passed);
    }
}

Section 5.9.7 Retired FRQ - Arrays - ArrayTester - Part A

The following is a free response question from 2018. It was question 4 on the exam. You can see all the free response questions from past exams at Past AP CSA Exams.

Question 4. This question involves reasoning about arrays of integers. You will write two static methods, both of which are in a class named ArrayTester.

public class ArrayTester
{
    /**
     * Returns an array containing the elements of column c of arr2D in the same
     * order as they appear in arr2D. Precondition: c is a valid column index in
     * arr2D. Postcondition: arr2D is unchanged.
     */
    public static int[] getColumn(int[][] arr2D, int c)
    {
        /* to be implemented in part (a) */
    }

    /**
     * Returns true if and only if every value in arr1 appears in arr2.
     * Precondition: arr1 and arr2 have the same length. Postcondition: arr1 and
     * arr2 are unchanged.
     */
    public static boolean hasAllValues(int[] arr1, int[] arr2)
    {
        /* implementation not shown */
    }

    /** Returns true if arr contains any duplicate values; false otherwise. */
    public static boolean containsDuplicates(int[] arr)
    {
        /* implementation not shown) */
    }

    /**
     * Returns true if square is a Latin square as described in part (b); false
     * otherwise. Precondition: square has an equal number of rows and columns.
     * Precondition: square has at least one row.
     */
    public static boolean isLatin(int[][] square)
    {
        /* to be implemented in part (b) */
    }
}

Part a. Write a static method getColumn, which returns a one-dimensional array containing the elements of a single column in a two-dimensional array. The elements in the returned array should be in the same order as they appear in the given column. The notation arr2D [r][c] represents the array at row r and column c.

The following code segment initializes an array and calls the getColumn method.

int [] [] arr2D = { { 0, 1, 2 }, { 3, 4, 5 }, { 6, 7, 8 }, { 9, 5, 3 }};
int[] result = ArrayTester.getColumn (arr2D, 1);

When the code segment has completed execution, the variable result result will have the following contents. result: {1, 4, 7, 5}

Subsection 5.9.7.1 Try and Solve It

Activity 5.9.34.

Complete the method getColumn below.

public class ArrayTester
{

/**
     * Returns an array containing the elements of column c of arr2D in the same
     * order as they appear in arr2D. Precondition: c is a valid column index in
     * arr2D. Postcondition: arr2D is unchanged.
     */
    public static int[] getColumn(int[][] arr2D, int c)
    {
        /** Complete this method * */
    }

// Main method to test getColumn method
    public static void main(String[] args)
    {
        int[][] arr2D = { {0, 1, 2}, {3, 4, 5}, {6, 7, 8}, {9, 5, 3}};
        int[] result = ArrayTester.getColumn(arr2D, 1);
        System.out.println(
                "It should print the values from the second column: 1 4 7 5.");
        for (int i = 0; i < result.length; i++)
        {
            System.out.print(result[i] + " ");
        }
    } // end of main
} // end of class
====
import static org.junit.Assert.*;

import org.junit.*;

import java.io.*;
import java.util.Arrays;

// import java.util.ArrayList;

public class RunestoneTests extends CodeTestHelper
{
    public RunestoneTests()
    {
        super("ArrayTester");
        // CodeTestHelper.sort = true;
    }

@Test
    public void testMain1()
    {
        boolean passed = false;

String expect = "It should print the values from the second column: 1 4 7 5.\n1 4 7 5";

String output = getMethodOutput("main");

passed = getResults(expect, output, "Checking for expected output from main");
        assertTrue(passed);
    }

@Test
    public void testMain2()
    {
        boolean passed = false;

int[][] arr2D = { {0, 1, 2}, {3, 4, 5}, {6, 7, 8}, {9, 5, 3}};

String arrayStr = "[[0, 1, 2],\n [3, 4, 5],\n [6, 7, 8],\n [9, 5, 3]]";

int[] result = ArrayTester.getColumn(arr2D, 0);

String expect = "[0, 3, 6, 9]";
        String output = Arrays.toString(result);

passed =
                getResults(
                        expect,
                        output,
                        "Checking for expected output for getColumn(arr2D, 0)\n" + arrayStr);
        assertTrue(passed);
    }

@Test
    public void testMain3()
    {
        boolean passed = false;

int[][] arr2D = { {0, 1, 2, 3, 4, 5}, {6, 7, 8, 9, 5, 3}};

String arrayStr = "[[0, 1, 2, 3, 4, 5],\n [6, 7, 8, 9, 5, 3]]";

int[] result = ArrayTester.getColumn(arr2D, 2);

String expect = "[2, 8]";
        String output = Arrays.toString(result);

passed =
                getResults(
                        expect,
                        output,
                        "Checking for expected output for getColumn(arr2D, 0)\n" + arrayStr);
        assertTrue(passed);
    }
}

Section 5.9.8 Retired FRQ - Arrays - ArrayTester - Part B

Arrays are no longer part of an assigned FRQ. However, they are good practice with reading and answering FRQs.

Part b. Write the static method isLatin, which returns true if a given two-dimensional square array is a Latin square, and otherwise, returns false.

A two-dimensional square array of integers is a Latin square if the following conditions are true. 1) The first row has no duplicate values. 2) All values in the first row of the square appear in each row of the square. 3) All values in the first row of the square appear in each column of the square.

The ArrayTester class provides two helper methods: containsDuplicates and hasAllValues. The method containsDuplicates returns true if the given one-dimensional array arr contains any duplicate values and false otherwise. The method hasAllValues returns true if and only if every value in arr1 appears in arr2. You do not need to write the code for these methods.

Complete method isLatin below. Assume that getColumn works as specified, regardless of what you wrote in part (a). You must use getColumn, hasAllValues, and containsDuplicates appropriately to receive full credit.

Subsection 5.9.8.1 Try and Solve It

Activity 5.9.35.

Complete the method isLatin below.

public class ArrayTester
{

public static boolean isLatin(int[][] square)
    {
        // put your solution here

}

/** Copy in your solution of getColumn from the previous section */
    public static int[] getColumn(int[][] arr2D, int c)
    {
        // put your solution here

}

// Main method to test getColumn method
    public static void main(String[] args)
    {
        int[][] arr2D = { {1, 2, 3}, {2, 3, 1}, {3, 1, 2}};
        boolean test = isLatin(arr2D);
        System.out.println(
                "If isLatin is implemented correctly, then test should be true:"
                        + test);
        if (!test)
        {
            System.out.print(
                    "Uh oh! isLatin(test) was false, but it should be true.");
        }
        else
        {
            System.out.println("Correct!");
        }
    } // end of main

/** Returns true if and only if every value in arr1 appears in arr2. */
    public static boolean hasAllValues(int[] arr1, int[] arr2)
    {

boolean[] flags = new boolean[arr1.length]; // default values false

for (int i = 0; i < arr1.length; i++)
        {
            for (int j = 0; j < arr2.length; j++)
            {
                if (arr1[i] == arr2[j])
                {
                    flags[i] = true;
                }
            }
        }
        for (boolean b : flags)
        {
            if (b == false)
            {
                return false;
            }
        }
        return true;
    }

/** Returns true if arr contains any duplicate values; false otherwise. */
    public static boolean containsDuplicates(int[] arr)
    {
        for (int i = 0; i < arr.length - 1; i++)
        {
            for (int j = i + 1; j < arr.length; j++)
            {
                if (arr[i] == arr[j])
                {
                    return true;
                }
            }
        }
        return false;
    }
} // end of the class
====
import static org.junit.Assert.*;

import org.junit.*;

import java.io.*;

// import java.util.ArrayList;

public class RunestoneTests extends CodeTestHelper
{
    public RunestoneTests()
    {
        super("ArrayTester");
        // CodeTestHelper.sort = true;
    }

@Test
    public void testMain1()
    {
        boolean passed = false;

String expect =
                "If isLatin is implemented correctly, then test should be true:true\nCorrect!";

String output = getMethodOutput("main");

passed = getResults(expect, output, "Checking for expected output from main");
        assertTrue(passed);
    }

@Test
    public void testMain2()
    {
        boolean passed = false;

int[][] arr2D = { {1, 2, 3}, {2, 3, 1}, {3, 1, 2}};

String arrayStr = "[[1, 2, 3],\n [2, 3, 1],\n [3, 1, 2]]";

String expect = "true";
        String output = "" + ArrayTester.isLatin(arr2D);

passed =
                getResults(
                        expect,
                        output,
                        "Checking for expected output for isLatin(arr2D)\n" + arrayStr);
        assertTrue(passed);
    }

@Test
    public void testMain3()
    {
        boolean passed = false;

int[][] arr2D = { {1, 2, 3}, {2, 3, 1}, {7, 8, 9}};

String arrayStr = "[[1, 2, 3],\n [2, 3, 1],\n [7, 8, 9]]";

String expect = "false";
        String output = "" + ArrayTester.isLatin(arr2D);

passed =
                getResults(
                        expect,
                        output,
                        "Checking for expected output for isLatin(arr2D)\n" + arrayStr);
        assertTrue(passed);
    }
}

Section 5.9 Free Response Questions

Section 5.9.1 Free Response - Trio A

Subsection 5.9.1.1 Try and Solve It

Activity 5.9.1.

Section 5.9.2 Trio Student Solution 1

Subsection 5.9.2.1 Grading Rubric

Subsection 5.9.2.2 Practice Grading

Activity 5.9.2.

Activity 5.9.3.

Activity 5.9.4.

Activity 5.9.5.

Activity 5.9.6.

Activity 5.9.7.

Activity 5.9.8.

Activity 5.9.9.

Activity 5.9.10.

Activity 5.9.11.

Section 5.9.3 Trio Student Solution 2

Subsection 5.9.3.1 Grading Rubric

Subsection 5.9.3.2 Practice Grading

Activity 5.9.12.

Activity 5.9.13.

Activity 5.9.14.

Activity 5.9.15.

Activity 5.9.16.

Activity 5.9.17.

Activity 5.9.18.

Activity 5.9.19.

Activity 5.9.20.

Activity 5.9.21.

Section 5.9.4 Trio Student Solution 3

Subsection 5.9.4.1 Grading Rubric

Subsection 5.9.4.2 Practice Grading

Activity 5.9.22.

Activity 5.9.23.

Activity 5.9.24.

Activity 5.9.25.

Activity 5.9.26.

Activity 5.9.27.

Activity 5.9.28.

Activity 5.9.29.

Activity 5.9.30.

Activity 5.9.31.

Section 5.9.5 Retired FRQ - Inheritance - NumberGroup - Part B

Subsection 5.9.5.1 Try and Solve It

Activity 5.9.32.

Section 5.9.6 Retired FRQ - Inheritance - NumberGroup - Part C

Subsection 5.9.6.1 Try and Solve It

Activity 5.9.33.

Section 5.9.7 Retired FRQ - Arrays - ArrayTester - Part A

Subsection 5.9.7.1 Try and Solve It

Activity 5.9.34.

Section 5.9.8 Retired FRQ - Arrays - ArrayTester - Part B

Subsection 5.9.8.1 Try and Solve It

Activity 5.9.35.