CS360 - practice

Practice w23hm2q1

2024-10-18T00:00:00+05:00

CRC Cards

Engage in Object-Oriented Analysis and read the following scenario paragraph and pull out potential nouns that may lead to classes and verbs may lead to methods or relationships.

Make CRC cards to model each meaningful class relevant to the problem and scenario. Collaborators and responsibilities must be described.

You may use plain text, and separate the cards by a blank line. The following format is recommended:

Class: X

Collaborator: Y

Collaborator: Z

Responsibility: K

Responsibility: L

Responsibility: M

I want to track my tea collection. I collect tea. I use TeaBox app to track my tea and to make trades of tea with other users: I propose a trade and if the other player accepts then we email each other. Some teas cannot be consumed if they are too old, so I need to be warned when tea in my collection needs to be consumed. Some teas are meant to age and I don’t need warnings but I need to know their age. When I completely consume a tea, it should be removed from the active collection into the archived collection, as I would like to keep a record of past teas.

Practice w23hm2q2

2024-10-18T00:00:00+05:00

Model-View (UML)

Interpret the Java code below. It represents a pressure cooker, like the instant-pot. It’s a device that heats up food while under pressure. It provides an API to monitor the pressure and temperature of the pressure cooker. Currently class PressureCooker monitors pressure and temperature, draws a pressure gauge, graphs pressure over time, and draws a thermometer of the temperature. We want to add a temperature graph. Unfortunately we seem to be making this class too big.

Refactor/restructure this code AS A UML CLASS DIAGRAM OF RESTRUCTURED CODE to implement the Model-View pattern (variation of the MVC pattern, but without a dedicated Controller). Separate out models and views, and add new views as necessary to address the new features that were asked for. Explicitly improve cohesion with your restructuring of the code. You can make new classes and interfaces, you can move methods, rename methods, and make new methods.

Add temperature graph
Restructure into MVC using just models and views
Improve Cohesion

On the diagram, CLEARLY LABEL which class(es) represents the Model and the View components. You do NOT need to have a Controller.

Draw a well-designed UML class diagram to represent this information. Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate. "..." means much code is omitted.

import java.util.*;
class PressureCooker {
    private double pressure;
    private double temperature;
    private LinkedList<Double> pastPressures;
    public double currentPressure() { return pressure; }
    /* called by the hardware driver */
    protected void setPressure(double p) {
        pastPressures.push(Double.valueOf(pressure));
        pressure = p;
                draw();
    }
    // drawPressureGauge draws a pressure gauge based on the
    // current value of pressure
    public void drawPressureGauge() {
        /* ... */
    }
    // drawPressureGraph draws a plot of pressure over time.
    public void drawPressureGraph() {
        /* ... */
    }
    // drawThermometer draws a thermometer representing the
    // temperature
    public void drawThermometer() {
        /* ... */
    }
    public void draw() {
        drawPressureGauge();
        drawPressureGraph();
        drawThermometer();
    }
}

Practice w23hm1 Answers

2024-09-19T00:00:00+05:00

Practice w23hm1 Answers Videos:

Practice W23HM1 Answers Videos

Practice w23am1q1

2024-09-12T00:00:00+05:00

Java to UML Class Diagram

Convert this Java code to a UML class diagram. This Java code is meant to represent passengers and buses in the fictional world of My Neighbour Totoro. A Catbus can take passengers to places like a regular bus, but it also behaves like a cat. There is one specific kind of passenger (Totoro) that can ask the Catbus to do things for him.

public abstract class Bus {
    private String sign; // destination sign (e.g. "Hospital")
    private ArrayList<Passenger> passengers;
    public Bus(String sign) {
        this.sign = sign;
        this.passengers = new ArrayList<Passenger>();
    }
    public abstract void load(Passenger p);
    public abstract boolean travel(Location from, Location to);
}

public interface CatLike {
    public void purr();
}

public class CatBus extends Bus implements CatLike {
    public CatBus(String sign) {
        super(sign);
    }
    public void load(Passenger p) {
        // ...
    }
    public boolean travel(Location from, Location to) {
        // ...
        return true;
    }
    public void purr() {
        // ...
    }
}

public interface Location {
    // ...
}


public interface Passenger {
    // ...
}

public class Totoro implements Passenger {
    // Totoro is the only King of the Forest
    // He doesn’t only ride Catbuses, but can control them
    public void controlCatBus(CatBus bus) {
        // ...
    }
}

Practice w23am1q2

2024-09-12T00:00:00+05:00

UML Class Diagram to Java

Convert this UML class diagram about the Harry Potter universe to skeletal Java Code. Include all attributes and obviously public methods. Make sure all required methods are implemented. Include all generalizations and necessary associations. You may use ellipses (...) to indicate there is some code in the method but it's a midterm and who has time to write that code!

ACCOMMODATIONS: If you need a textual version of this UML Q2.pdf and Q2.svg are available for you

Practice w23am1q3

2024-09-12T00:00:00+05:00

Liskov Substitution Principle

This Java code is poor! It violates the Liskov Substitution principle!

Restructure this code as UML and draw a UML Class Diagram of restructured code that doesn't violate the Liskov Substitution principle.

Draw a well-designed UML class diagram to represent this information. Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate.

"...” means much code is omitted.

This Java code is about quizzes (similar to eClass quizzes).

Be sure to leave a note on the diagram highlighting how you address the violation

class Quiz {
    protected Question[] questions;

    // ...

    public void printAnswerKey() {
        for (int i = 0; i < questions.length; i++) {
            System.out.println(questions[i].getCorrectAnswer());
        }
    }
}

class Exam extends Quiz {
    protected Room room; // unlike quizzes, exams are administered in a room

    // ...
}

class Question {
    protected String question;

    protected String[] answers; // choices
    protected int correctAnswer; // index of a correct answer

    // ...

    public int getCorrectAnswer() {
        return correctAnswer;
    }
}

class EssayQuestion extends Question {
    // ...

    public int getCorrectAnswer() {
        System.err.println("Essay questions do not have a correct answer.");
        return -1;
    }
}

Practice w23am2q1

2024-09-12T00:00:00+05:00

CRC Cards

Engage in Object-Oriented Analysis and read the following scenario paragraph and pull out potential nouns that may lead to classes and verbs that may lead to methods or relationships.

Make CRC cards to model each meaningful class relevant to the problem and scenario. Collaborators and responsibilities must be described.

You may use plain text, and separate the cards by a blank line. The following format is recommended:

Class: X

Collaborator: Y

Collaborator: Z

Responsibility: K

Responsibility: L

Responsibility: M

I see that the class that I take is scheduled in TEL 150. I have never taken a class in this classroom before, so I open the RateMyUofAClassroom app. It shows a long list of rooms. I start typing “TEL 1”, and the app suggests “TEL 150”. I click it and see that this classroom has an average rating of 4.3, nice! I go to my class and actually like the room a lot. I open the app and give the room a 5. The average rating is updated, it's now 4.4! What if I try to rate it again? No, I get an error message saying "You have already rated this classroom.”

Practice w23am2q2

2024-09-12T00:00:00+05:00

Model-View (UML)

Interpret the Java code below. It represents an automated parking lot system. It provides an API to monitor the status of a parking lot. Currently, the ParkingLot class can display available parking spots and draw the parking lot map. We want to add a pie chart showing the current ratio of available and occupied parking spots. Unfortunately, we seem to be making this class too big.

Refactor/restructure this code AS A UML CLASS DIAGRAM OF RESTRUCTURED CODE to implement the Model-View pattern (variation of the MVC pattern, but without a dedicated Controller). Separate out models and views, and add new views as necessary to address the new features that were asked for. Explicitly improve cohesion with your restructuring of the code. You can make new classes and interfaces, you can move methods, rename methods, and make new methods.

Add a pie chart
Restructure into MVC using just models and views.

On the diagram, CLEARLY LABEL which class(es) represents the Model and the View components. You do NOT need to have a Controller.

Do NOT submit Java, submit UML!

import java.util.*;


class ParkingLot {
    private int capacity;
    private int numCars;
    private HashMap<Integer, Boolean> spots;

    /* ... */

    /* called by the parking detection system */
    protected void carIn(int spot) {
        spots.put(spot, true);
        numCars++;
        render();
    }

    /* called by the parking detection system */
    protected void carOut(int spot) {
        spots.put(spot, false);
        numCars--;
        render();
    }

    // lists available parking spots
    public void listSpots() {
        /* ... */
    }

    // draws a map of the parking spots and their status
    public void drawMap() {
        /* ... */
    }

    public void render() {
        listSpots();
        drawMap();
    }
}

Practice w23am2q3

2024-09-12T00:00:00+05:00

Use Case

Write a use case for the task of a young person applying for a job based on the following scenario.

I am 16 years old and looking for my first job, so I go to the MyFirstJob website. The website shows that the minimum age to work in Alberta is 15 and asks for my date of birth. I enter "2007-01-23". On the next page, there is a map showing all employers with current job openings. I use a filter to select the "Food" category. I see that a local coffee shop in my neighbourhood, "Café con Sabor," is looking for a part-time barista. I know a lot about coffee from my parents, so this sounds like a good fit! I click on "Café con Sabor" and see the application form. I go ahead and fill it out. Then I have to upload a resume. I try to upload my resume in DOCX format, but I get an error message: "Only PDF is supported". I upload the PDF, and the site displays the message "Application submitted!" and a happy face emoticon.

Include the following elements:

Use case name
Participating actors
Goal
Trigger
Preconditions
Postconditions
Basic flow
One exception

Practice w23hm1q1

2024-09-12T00:00:00+05:00

Java to UML Class Diagram

Convert this Java code to a UML class diagram. This Java code is meant to represent a mouth tasting and consuming food. There are food, flavours, tongues, and taste buds.

import java.util.*;

class Mouth {
    Collection<Tooth> teeth;
    Tongue tongue;
    // ...
}
class Tooth {
    // ...
}
class Tongue {
    private TasteBud[] buds;
    Flavour taste(Food f) {
        Flavour[] flavours = new Flavour[buds.length];
        for (int i = 0; i < buds.length; i++) {
            flavours[i] = buds[i].taste(f);
        }
        return new AggregateFlavour(flavours);
    }
    // ...
}
interface TasteBud {
    public Flavour taste(Food f);
}
interface Flavour {
    public int sweet();
    public int salty();
}
class AggregateFlavour implements Flavour {
    Flavour[] flavours;
    AggregateFlavour(Flavour[] flav) {
        flavours = flav;
    }
    public int sweet() {
        // Sum of sweetness
        // ...
    }
    public int salty() {
        // Sum of salty
        // ...
    }
    // ...
}
interface Food {
    // ...
}

Practice w23hm1q2

2024-09-12T00:00:00+05:00

UML Class Diagram to Java

Convert this UML class diagram about the parameciums (a fancy microbe) to skeletal Java Code. Include all attributes and obviously public methods. Make sure all required methods are implemented. Include all generalizations and necessary associations. You may use ellipses (...) to indicate there is some code in the method but it's a midterm and who has time to write that code!

ACCOMMODATIONS: If you need a textual version of this UML output.pdf is available for you.

Practice w23hm1q3

2024-09-12T00:00:00+05:00

Liskov Substitution Principle

This Java code is poor! It violates the Liskov Substitution principle!

Restructure this code as UML and draw a UML Class Diagram of restructured code that doesn't violate the Liskov Substitution principle.

Draw a well-designed UML class diagram to represent this information. Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate.

"...” means much code is omitted.

This Java code is about Monsters in a video game.

Be sure to leave a note on the diagram highlighting how you address the violation

interface Monster {
    // move object to x, y
    public void translate(double x, double y);
    public void draw();
}
// Blob is an amphorous pile of goo
class Blob implements Monster {
    public void translate(double x, double y) { /* ... */ }
    public void draw() { /* ... */ }
    // ...
}
// ImmobileBlob is the blob that doesn't move!
class ImmobileBlob extends Blob {
    private int x;
    private int y;
    ImmobileBlob(int x, int y) { /* ... */ }
    public void translate(double x, double y) {
        // do nothing
    }
    // ...
}
class GameCanvas {
    // ...
    // translate the monsters into a 16 x 16 grid
    void gridify(Monster[] xs) {
        for (int i = 0; i < xs.length; i++) {
            xs[i].translate(i / 16, i % 16); // % is modulus
            xs[i].draw();
        }
    }
}

Practice w23hpmq1

2024-09-11T00:00:00+05:00

Convert this Java code to a UML class diagram. This Java code is meant to represent a animals. Draw a well-designed UML class diagram to represent this information. Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate.

"..." means much code is omitted.

class Animal {
    protected String name;
    protected int age;
    public String getName() { return name; }
}

interface Predator {
    public boolean hunt(Animal a);
}

interface Herbivore {
    public void eat(Plant p);
}

class Lion extends Animal implements Predator {
    public boolean hunt(Animal a) {
        // ...
    }
    // ...
}

class Zebra extends Animal implements Herbivore {
    protected int stripes;
    public void eat(Plant p) {
        // ...
    }
}

class Savannah {
    private int area;
    private Lion alphaLion;
    protected ArrayList<Animal> inhabitants = new ArrayList<Animal>();
}

Practice w23am3q1

2024-09-03T00:00:00+05:00

Scenario to Sequence Diagram

Convert this scenario into a sequence diagram. Remember to include all the actors, components, lifelines, activation boxes and guards (conditions). Use good names for the methods.

My car needs gas, so I drive to the nearest gas station. I swipe my debit card at the pump. The pump connects to the processing center to authorize the card for the default amount of $100, and if there are sufficient funds in my account, the processing center confirms successful authorization. Next, I select Regular and the pump dispenses the selected grade of gasoline. It then asks the processing center to charge my card and receives a transaction ID in response. The pump asks if I want a receipt. The pump prints a receipt only if I tap Yes.**

Practice w23am3q2

2024-09-03T00:00:00+05:00

Template Method Pattern Refactoring (Java Code to UML Class Diagram)

This code represents a training program that includes two different types of workouts (cardio and strength training).

Restructure this code with the template method pattern and provide a UML class diagram depicting the structure and operations one would expect after refactoring this code to use a template method pattern. Your solution must significantly reduce code duplication and enhance reuse.

You must provide the template method Java code in a UML comment (see example below).

Draw the resulting UML class diagram of the refactored code. Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate.

class CardioWorkout {
    public void doCardioWorkout() {
        warmUp();
        run();
        stretch();
    }

    private void warmUp() {
        System.out.println("Warming up.");
    }


    private void run() {
        System.out.println("Running.");
    }


    private void stretch() {
        System.out.println("Stretching.");
    }
}

class StrengthWorkout {  
        public void doStrengthWorkout() {
            warmUp();
            doPushUps();
            doSquats();
            stretch();
        }

        private void warmUp() {
            System.out.println("Warming up.");
        }


        private void doPushUps() {
            System.out.println("Doing push ups.");
        }


        private void doSquats() {
            System.out.println("Doing squats.");
        }


        private void stretch() {
            System.out.println("Stretching.");
        }
}

Practice w23am3q3

2024-09-03T00:00:00+05:00

Adapter Design Pattern Refactoring (UML class diagram)

The code represents the university HR system. There are employees paid hourly (support staff, secretaries, assistants etc.) and students. Some students can be employed as teaching assistants. In this case, their hourly rate depends on their year. The Report class prepares reports on employees and teaching assistants.

There is a problem with the Report class as it knows too much about students!

Restructure this code with the Object Adapter design pattern and provide a UML class diagram depicting the structure and operations one would expect after refactoring this code to use an object adapter.

In your solution, the Report class must have one (and only one) method. Your solution must significantly reduce code duplication and enhance reuse.

Draw the resulting UML class diagram of the refactored code. Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate.**

class Employee {
    private String name;
    private String jobTitle;
    private double hourlyRate;
    public String getName() { return name; }
    public String getJobTitle() { return jobTitle; }
    public double getHourlyRate() { return hourlyRate; }
}

class Student {
    private String name;
    private String major;
    private int year;
    public String getName() { return name; }
    public String getMajor() { return major; }
    public int getYear() { return year; }
}

class Report {
    // Prints report for an employee (hourly staff)
    public void employeeReport(Employee e) {
        System.out.println("Name: " + e.getName());
        System.out.println("Job Title: " + e.getJobTitle());
        System.out.println("Hourly Rate: " + e.getHourlyRate());
    }

    // Prints report for a teaching assistant
    public void studentReport(Student s) {
        System.out.println("Name: " + s.getName());
        System.out.println("Job Title: Teaching Assistant");
        double hourlyRate = 0;
        if (s.getYear() == 1) {
            hourlyRate = 17;
        } else if (s.getYear() <= 3) {
            hourlyRate = 18;
        } else {
            hourlyRate = 19;
        }
        System.out.println("Hourly Rate: " + hourlyRate);
    }
}

Practice w23hm3q1

2023-03-29T00:00:00+05:00

Midterm 3 Question 1 (March 29) -- Hindle

Submit a PDF, PNG or JPEG

5 marks

You must add your CCID to your answer

Adapter and Sequence Diagram

You’ve written an object adapter (RTFAdapter) to adapt rich text files to an interface compatible with plain text files. Show your adaptation via a UML sequence diagram. Remember to include all the actors, components, lifelines, iteration, and activation boxes. Use good names for the methods.

We want to read the lines of a RichTextFile (RTF), but RichTextFile—which we got from a 3rd party library—doesn’t implement the same interface. You’ve implemented an object adapter so we can use the ReadOutLoud class to read out loud (readText) a RichTextFile.

Show a sequence diagram of Driver.run() operating with an object adapter (RTFAdapter) that adapts a RichTextFile to a TextLineReader.
RTFAdapter is an object adapter

interface TextLineReader {
    // while ! isEndOfile() you can call readNextLine                   
     public boolean isEndOfFile();    
     // move forward 1 line of text, read it, and return it.    
     public String readNextLine();
}
class PlainTextFile implements TextLineReader {
    public PlainTextFile(String file) { /* ... */ }
    public boolean isEndOfFile() { /* ... */ }
    public String readNextLine() { /* ... /; }
    / ... /
}
class RichTextFile {
    public RichTextFile(String file) { / ... */ }
    // How many lines in the RTF
    public int totalLines() { /* ... */ }
    // Return a specific line
    public String readLine(int i) { /* .../ }
    / ... /
}
class ReadOutLoud {
    public void readText(TextLineReader r) {
        while( ! r.isEndOfFile() ) {
                sayTheLine( r.readNextLine() );
        }
    }
    public void sayTheLine( String s) { / ... / }
    / ... /
}
class RTFAdapter implements TextLineReader {
    RTFAdapter(RichTextFile rtf) { / ... / }
    public boolean isEndOfFile() { / ... / }
    public String readNextLine() { / ... / }
    / ... */
}
public class Driver {
    public static void run() {
        new ReadOutLoud().readText(
            new RTFAdapter(
                new RichTextFile("text.rtf")
            )
        );
    }
}

Practice w23hm3q2

2023-03-29T00:00:00+05:00

Midterm 3 Question 2 (March 29) -- Hindle

Submit a PDF, PNG or JPEG

5 marks

You must add your CCID to your answer

Template Method Pattern Refactoring (Java Code to UML Class Diagram)

This code represents code that establishes an encrypted connection using TLS 1.2 or TLS 1.3 protocols. TLS 1.3 is faster to establish than TLS 1.2 because it does more work in fewer messages.

Restructure this code with the template method pattern and provide a UML class diagram depicting the structure and operations one would expect after refactoring this code to use a template method. Your solution must significantly reduce code duplication and enhance reuse.

You must provide the template method Java code in a UML comment (see example below).

Draw the resulting UML class diagram of the refactored code. Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate. "...” or “/ … /” means much code is omitted.

interface Socket {
    /* ... /
}
class TLS12 {
    Socket socket = null;
    Socket encryptLink(Socket s) {
        this.socket = s;
        clientHello();
        serverHello();
        csKeyExchange();
        return wrapSock();
    }
    void clientHello() { / ... / }
    void serverHello() { / ... / }
    void csKeyExchange() { / ... / }
    Socket wrapSock() { / ... / }
    / ... /
}
class TLS13 {
    Socket socket = null;
    Socket encryptLink(Socket s) {
        this.socket = s;
        clientHello();
        serverHelloWExchange();
        return wrapSock();
    }
    void clientHello() { / ... / }
    void serverHelloWExchange() { / ... / }
    Socket wrapSock() { / ... */ }
}

Practice w23hm3q3

2023-03-29T00:00:00+05:00

Midterm 3 Question 3 (March 29) -- Hindle

Submit a PDF, PNG or JPEG

5 marks

You must add your CCID to your answer

Dependency Injection with Singleton Pattern (UML class diagram)

This code represents the attempt to test a networked toaster. But we’re having a hard time testing it because we used the singleton pattern. Combine dependency injection with the singleton pattern so we can inject a mock object as the singleton. Provide a UML class diagram depicting the structure and operations one would expect after refactoring this code to allow dependency injection on the singleton. You cannot modify ToastCommand, or MockToaster. Modify the singleton with dependency injection.

You must provide the 1 line of Java code that we need to add in ToastCommandTest.testOnFire in a UML comment (see example below).

Draw the resulting UML class diagram of the refactored code, including the . Provide the basic abstractions, attributes, methods, relationships, multiplicities, and navigabilities as appropriate. "...” or “/ … /” means much code is omitted.

class Toaster {
    /* We have control over this class /
    private static Toaster instance = new Toaster();
    protected Toaster() { / ... / }
    public static Toaster getInstance() {
        return instance;
    }
    // tells us if the toaster is on fire.
    public boolean onFire() { / ... / }
    / ... /
}
class ToastCommand {
    // do not modify this class
    void toast() {
        Toaster p = Toaster.getInstance();
        if (p.onFire()) { // test the code inside this if block
            throw new ToasterOnFireException("Toaster Meltdown");
        }
        / ... /
    }
}
class MockToaster extends Toaster {
    // do not modify this class
    MockToaster() { / ... / }
    public boolean onFire() { return true; }
    / ... */
}
class ToastCommandTest {
    // modify 1 line of this class
    void testOnFire() {
        ToastCommand t = new ToastCommand();
        MockToaster mock = new MockToaster();
                                           // fill in this line
        try {
            t.toast();
            assert( false ); // shouldn't reach here
        } catch (ToasterOnFireException e) {
            assert( true );
        }
    }
}

Practice w23hm2q3

2023-03-01T00:00:00+05:00

Midterm 2 Question 3 (March 29) -- Hindle

Plain text preferred. Alternatively, submit PDF, PNG or JPEG

5 marks

You must add your CCID to your answer

Use Case

Write a use case for the task of a young person applying for a job based on the following scenario.

I open up the JobRoulette app. The app asks me to provide demographic information including my name and age. Then it asks about education, which I describe my high school diploma and 1 bachelor's degree in actuarial sciences from the University of Waterloo. After that it provides me with a list of 4 categories of skills, I click on IT skills. It provides a list of technologies and asks me to click on ones I am familiar with, I click MS Office, Excel, and Raid Shadow Legends. I submit those skills and the app shows me 3 brief job descriptions. I click on one, it shows me details, and I’m not interested so I click decline. I click on the next one “VPN promoter”. Based on the details it seems to be relevant to my interests and so I click apply. The app tells me that it has submitted my application.

Include the following elements:

Use case name
Participating actors
Goal
Trigger
Preconditions
Postconditions
Basic flow
One exception