8.4.2. Free Response - Climbing Club A¶

The following is part a of a free response question from 2012. It was question 1 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.

Question 1. A mountain climbing club maintains a record of the climbs that its members have made. Information about a climb includes the name of the mountain peak and the amount of time it took to reach the top. The information is contained in the ClimbInfo class as declared below.

public class ClimbInfo
{
    /**
     * Creates a ClimbInfo object with name peakName and time climbTime.
     *
     * @param peakName the name of the mountain peak
     * @param climbTime the number of minutes taken to complete the climb
     */
    public ClimbInfo(String peakName, int climbTime)
    {
        /* implementation not shown */
    }

    /**
     * @return the name of the mountain peak
     */
    public String getName()
    {
        /* implementation not shown */
    }

    /**
     * @return the number of minutes taken to complete the climb
     */
    public int getTime()
    {
        /* implementation not shown */
    }

    // There may be instance variables, constructors, and methods
    // that are not shown.
}

The ClimbingClub class maintains a list of the climbs made by members of the club. The declaration of the ClimbingClub class is shown below. You will write two different implementations of the addClimb method. You will also answer two questions about an implementation of the distinctPeakNames method

public class ClimbingClub
{
    /**
     * The list of climbs completed by members of the club. Guaranteed not to be
     * null. Contains only non-null references.
     */
    private List<ClimbInfo> climbList;

    /** Creates a new ClimbingClub object. */
    public ClimbingClub()
    {
        climbList = new ArrayList<ClimbInfo>();
    }

    /**
     * Adds a new climb with name peakName and time climbTime to the list of
     * climbs.
     *
     * @param peakName the name of the mountain peak climbed
     * @param climbTime the number of minutes taken to complete the climb
     */
    public void addClimb(String peakName, int climbTime)
    {
        /* to be implemented in part (a) */
    }

    /**
     * @return the number of distinct names in the list of climbs
     */
    public int distinctPeakNames()
    {
        /* implementation shown in part (c) */
    }

    // There may be instance variables, constructors, and methods
    // that are not shown.
}

Part a. Write an implementation of the ClimbingClub method addClimb that stores the ClimbInfo objects in the order they were added. This implementation of addClimb should create a new ClimbInfo object with the given name and time. It appends a reference to that object to the end of climbList. For example, consider the following code segment.

ClimbingClub hikerClub = new ClimbingClub();
hikerClub.addClimb("Monadnock", 274);
hikerClub.addClimb("Whiteface", 301);
hikerClub.addClimb("Algonquin", 225);
hikerClub.addClimb("Monadnock", 344);

When the code segment has completed executing, the instance variable climbList would contain the following entries.

Picture of the list after the above code executes

8.4.2.1. How To Solve This¶

Click to reveal the algorithm and practice problems to help you write your solution.

In the addClimb method you need to create a new ClimbInfo object and initialize the peakName and climbTime. How do you create a new object of a class and initialize the fields?

Once you have created the ClimbInfo object you want to add it in the order they were created. To do this you can add it to the end of the climbList. How do you add an object to the end of a list?

7-4-2-1: How would you create a new object newClimb of the ClimbInfo class, with a peakName of Everest and climbTime of 600?

ClimbInfo newClimb = new ClimbInfo("Everest", 600);
Correct!
new ClimbInfo("Everest", 600);
This answer is missing the instantiation of the variable newClimb. Try again!
ClimbInfo newClimb = new ClimbInfo();
The constructor of a ClimbInfo object requires two arguments. Try again!

7-4-2-2: How do you append a new item, 7, to the end of a non-empty ArrayList<Integer> list?

list.add(0, 7);
This would add 7 to the beginning of the list. Try again!
list.add(7);
Correct!
add(7);
You must reference the ArrayList list using a dot operator to use the add() method. Try again!

8.4.2.2. Try and Solve It¶

Complete the method addClimb in the ClimbingClub class in the code below. The code includes a main method that will test the addClimb method.

import java.util.ArrayList;
import java.util.List;

class ClimbInfo
{
    private String name;
    private int time;

/**
     * Creates a ClimbInfo object with name peakName and time climbTime.
     *
     * @param peakName the name of the mountain peak
     * @param climbTime the number of minutes taken to complete the climb
     */
    public ClimbInfo(String peakName, int climbTime)
    {
        name = peakName;
        time = climbTime;
    }

/**
     * @return the name of the mountain peak
     */
    public String getName()
    {
        return name;
    }

/**
     * @return the number of minutes taken to complete the climb
     */
    public int getTime()
    {
        return time;
    }

public String toString()
    {
        return "Peak name: " + name + " time: " + time;
    }
}

public class ClimbingClub
{
    /**
     * The list of climbs completed by members of the club. * Guaranteed not to be
     * null. Contains only non-null references.
     */
    private List<ClimbInfo> climbList;

/** Creates a new ClimbingClub object. */
    public ClimbingClub()
    {
        climbList = new ArrayList<ClimbInfo>();
    }

/**
     * Adds a new climb with name peakName and time climbTime to the end of the
     * list of climbs
     *
     * @param peakName the name of the mountain peak climbed
     * @param climbTime the number of minutes taken to complete the climb
     */
    public void addClimb(String peakName, int climbTime) {}

public String toString()
    {
        String output = "";
        for (ClimbInfo info : climbList)
        {
            output = output + info.toString() + "\n";
        }
        return output;
    }

public static void main(String[] args)
    {
        // test a
        ClimbingClub hikerClub = new ClimbingClub();
        hikerClub.addClimb("Monadnock", 274);
        hikerClub.addClimb("Whiteface", 301);
        hikerClub.addClimb("Algonquin", 225);
        hikerClub.addClimb("Monadnock", 344);
        System.out.print(hikerClub);
        System.out.println(
                "The order printed above should be Monadnock, Whiteface,"
                    + " Algonquin, Monadnock");
    }
}

====
import static org.junit.Assert.*;

import org.junit.*;

import java.io.*;

public class RunestoneTests extends CodeTestHelper
{

public RunestoneTests()
    {
        super("ClimbingClub");
    }

@Test
    public void testMain() throws IOException
    {
        String output = getMethodOutput("main");

String expect =
                "Peak name: Monadnock time: 274\n"
                    + "Peak name: Whiteface time: 301\n"
                    + "Peak name: Algonquin time: 225\n"
                    + "Peak name: Monadnock time: 344\n";

expect =
                expect
                        + "The order printed above should be Monadnock, Whiteface, Algonquin,"
                        + " Monadnock\n";

boolean passed = getResults(expect, output, "Expected output from main");
        assertTrue(passed);
    }

@Test
    public void test1()
    {
        ClimbingClub hikerClub = new ClimbingClub();
        hikerClub.addClimb("Monadnock", 274);
        hikerClub.addClimb("Whiteface", 301);
        hikerClub.addClimb("Algonquin", 225);
        hikerClub.addClimb("Monadnock", 344);

String output = hikerClub.toString();

boolean result = (output.compareTo(expect) == 0);

boolean passed =
                getResults(
                        "true",
                        "" + result,
                        "addClimb method works with arguments Monadnock: 274, Whiteface:301,"
                            + " Algonquin: 225, Monadnock: 344");

assertTrue(passed);
    }
}

8.4.2.3. Video - One way to code the solution¶

There are many possible solutions to this problem. The video below shows one solution.

The following video is also on YouTube at https://youtu.be/dAbU9_Qn92I. It walks through coding a solution.

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