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Episode 1: Abstractions on the mind

About this episode

Meet Jane Jones, a world famous OOP Researcher in OOP Programming. While on another expedition for the Secret Treasure of OOP, once again the trail runs cold. But this time, she stumbles upon a clue - an Ancient Relic, enscribed in OOP knowledge from days past hints at a new oppourtunity. What will develop from this finding?

As always, answers for the following questions can be found in the about section.

Practice Questions

1. Consider an application system controlling a bank, and one controlling a Game Console.

What different attributes would an Account class have in each of these examples?
Try producing UML diagrams for each class.

2. Consider an application to organise books in a bookstore, and an application used to manage book printing orders

What different attributes would a Book class have in each of these examples?
Try producing UML diagrams for each class.

3. Consider an application to manage printing documents, and an application to display documents.

What different attributes would a Document class have in each of these examples?
Try producing UML diagrams for each class.

Story Questions

For these questions, you will need to download the following application: Application Link

1. Using the template provided, try making your own book abstraction.

For now, try just including title. Once you are done, load it into the application, and view the results.
Template Link

2. It looks like some customers want to specify books by more than just their titles.

Try improving your abstraction by adding more fields.

3. Making an abstraction more specific is not always a good thing.

Try adding some irrelevant attributes to your abstraction, such as colour.
Why is this a bad decision?

4. Extension Question: Try building your own book record.

If you feel confident about the material covered so far, try building your own book managing system. Don't worry about making it like a library system, just build a simple system to manage personal books. Start with the Book class then make a BookManager class - use an ArrayList of Books and then add methods for searching, removing and adding books.
If you've managed all that, try adding a feature to keep track of loaned books.
Through this process you will learn how complex systems are built iteratively.

Practice Questions

1. Given the following class diagram, try producing corresponding Java code.

(Don't worry about method bodies).
Class Diagram

2. Given the following class diagram, try producing corresponding Java code.

(Don't worry about method bodies).
Class Diagram

3. Given the following class diagram, try producing corresponding Java code.

(Don't worry about method bodies).
Class Diagram

4. Extension Question: Try rebuilding the previous classes in another Object Oriented Language such as Python.

While the language used in this course is Java, the knowledge that you learn about Object Oriented programming should be applicable anywhere. If you feel that you are confident with the exercises covered so far, try applying them to another language. If you can do that successfully, then you have fully understood the concept.

Story Questions - Fixing the Management System

For these questions, you will need to download the following application: Application link

1. First, to fix the manager application, we'll need to reconstruct the account class.

Using the template provided, try creating a bank account class. Once you are done, load it into the application to view the results.
Template Link

2. Did you see that? It looks like there's another entity on the system..

And he seems to keep on removing your stored data. Remember those exercises on encapsulation?
Try implementing it here to fix the issue.

3. Extension Question: Try creating your own banking system.

If you are confident of the material covered so far, try constructing your own version of the banking system from scratch. As a hint, start with the bank account classes, then add a controller class to manage creating and adding accounts. This extension exercise will begin to teach you how to build bigger systems yourself.

Practice Questions

1.From the following UML diagram of a notebook and a textbook class in a book management system, try using abstraction to extract out common functionality into a parent class.

Remember, your parent class should have an appropriate name.
UML Diagram

2.From the following UML diagram of a mouse and keyboard class in a physical device management system, try using abstraction to extract out common functionality.

Remember, your parent class should have an appropriate name.
UML Diagram

3. From the following UML diagram of a driver and a car in a car hire management system, try extracting out common functionality.

Remember, your parent class should have an appropriate name.
UML Diagram

4. Extension Question: Try rebuilding the previous classes in another Object Oriented Language such as Python.

Story Questions

For these questions, you will need to download the following application: Application Link

1. To make a water plane, we need to first build some parts that are waterproof.

Using the template provided, produce a class of waterproof landing gear.
Template Link

2. Construct a plane that can land on water.

To make a functional plane, numerous factors, such as wind-speed, air-humidity, altitude all need to be taken into account, making the class very complex. However, as the plane model is already preprogramed into the model, we can make use of this code and reuse it for our water plane.
Use inheritance to construct your own water plane, except have it contain a copy of waterproof landing gear, and override the land method to call deploy on the new landing gear.
Try it out on the application when you are done.

3. Extension Question: Develop a system to play rock, paper, scissors.

If you are feeling confident in the material covered so far, the skills that you have learned so far should enable you to create your own rock, paper, scissors game.
Use a class to represent each player and to keep track of the score that they have. Then use a controller class to retrieve each player and ask them for a choice. This project will push your Java knoweldge.

Story Questions

For these questions, you will need to download the following application: Application Link

1.In order to make the ancient mechanism work, we'll need to re-implement it's checking methods.

Before we begin, using the template provided, construct your own mechanism class.
Template Link

2. Fix the ancient mechanism so it crushes rocks.

The problem at the moment, is that all the inputs to the sorter are passed to the key slot of the door.
For now, let's try stopping this by implementing a sort function which takes in rocks, and calls their crush method.
Try it out on the application when you are done.

3. Now, it seems like all the rocks are crushed.

This still causes issues, as we don't want to crush the ruby.
Can you think of a way to implement polymorphism to avoid this?
Try it out on the application when you are done.

4. Extension Question: Try Implementing Other types of Polymorphism.

In this course we mainly focus on overloading as an example of polymorphism, however, your Object Oriented knowledge wouldn't be complete without an exploration into the various other types of Polymorphism.
Try implementing a generic class that acts like a Queue using an arraylist.
Have a look into the various other kinds of polymorphism - did we cover all of them in our videos?

5. Extension Question: Try building a System in Python.

Java is a statically typed language, which means that every variable has to have a type, and every expression has to have a type which is evaluated at runtime. Java's strict typing mean that Object Oriented concepts are enforced rigorously in Java, making it a good language for teaching Object Oriented Programming. However Object Oriented Concepts are not restricted to static languages, and your Object Oriented tutoring would not be complete without some experience programming in an Dynamic Language.

Try building a system in Python. We recommend something simple like a dice rolling game.

Notice how certain OOP techniques are used less in dynamic languages, while others are more frequently used.
For example, without types, overloading can not occur, however, as there are no types, all functions are essentially generic.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. What attributes you will include in your simulation?

Bear in mind that particles have many attributes such as atomic composition, electrical charge, mass, but in this simulation not all these attributes matter as much.
Write down a list of attributes you might use in your simulation

2. Build an abstraction representing the object.

Using the template provided, try building your own particle class. For now, try giving it just an x and a y.
When you are done, load it into the application, and view the results.
Template Link

3. Improve your simulation by adding a mass attribute.

If you tried to generate a black hole, you would have noticed that the application indicates that it can't proceed as not all entities have mass.
This makes sense, as the key distinguishing factor of a black hole is its significant gravitational field.
Try adding a mass attribute to your abstraction of a particle.

4. Improve your simulation by adding a velocity attribute.

It seems that, despite all these changes, your particle still doesn't move.
Why is that – well, for the particle to be able to move, we need some way of tracking its velocity.
Try adding a velocity attribute for the x and y directions in your abstraction.

5. Extension Question: Try building a Particle Simulator in Java.

We actually constructed the entire application using Java and it's standard library. If you are feeling very confident with the material covered here so far, it would be good practice for your Object Oriented Programming skills if you tried creating your own Particle Simulator. In order to do this, you must first research into Swing, Java's GUI library. Try making a particle class and using Swing to draw the particle on the screen.
Try making the particle have a velocity and updating the particle's position based on it's velocity.
If you manage all that, you might want to look into threads to make the animations smoother.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. Construct a patient class to hold all the details about the patient.

To develop this system, the first thing we need to make, is a patient class to hold all the details about the patient.
Using the template provided, try constructing your own patient class. What attributes define a patient – make sure to include a name so that we can easily identify each patient. Once you are done, load the class into the application and view the result.
Template Link

2. Improve your model by adding symptoms for each patient.

Now, this system doesn't seem to do much – in order to provide functionality, we need to add a way of storing information about the patient's symptoms and some way to store the cure that we calculate.
Add a string array to each patient to store their symptoms.

3. It looks like there's a bug on the system - patient data is being changed.

It looks like there's a bug somewhere else in the system which messes with the patient data.
While one solution could be to fix the bug itself, but when working with systems as big as Watson, one developer only designs a small section of code.
Thus, it's our responsibility to make sure that, irrespective of what other people might try to do to our code, we make it work.
Try implementing encapsulation in this system to make it work. (Hint: try adding private)

4. Implement methods to selectively allow use of the private details.

Now the class is encapsulated, our code is protected, however now, even Watson can't access it.
We need some way of allowing people to view or modify only certain sections of our code. This can be done by implementing a getter and setter. . Consider patient symptoms – Watson needs access to it, so we can allow Watson access by implementing a getSymptoms function, which returns a copy of the application symptoms.
Try adding getters and setters for the other fields.

5. Extension Question: Try creating your own version of a Patient manager system from scratch.

Don't worry about visualizing the patients, just try creating a patient management system on the command line interface. Start with the patient class, then create the patient management class.

Functionality you could include would be the ability to add and remove patients, to add and remove symptoms from a patient, to show add and remove tests for a patient.
If you manage that, try also adding a new class for Doctors on your system. In this case you will need to refactor your code, to include inheritance between the Patient and the Doctor classes if they have any overlap.
In this process you will learn how in real-life systems, iteratively adding features sometimes means having to refactor your code to improve the structure of your objects.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. Construct a class to represent the new phone system.

First before we start developing the new phone system, we need to make a class to represent it.
Use the template provided to construct a class for your own version of the phone operating system.
Template Link

2. Improve your Operating System by inheriting from the base Android Operating System.

The android operating system is built upon layers of complexity, however, luckily for us, we can inherit the existing operating system to get all this code for free.
Modify your class to inherit the android operating system class.

3. Some base android features don't work with the new hardware. Can we fix it?

Looking at the simulator, it seems like some functions aren't working on the new phone – this is because the code in the old android operating system didn't know about the new features in the latest phone.
Let's try and fix that.
First override the takePhoto method to use the camera variable in your OS.

4. Now override the initialization method of the operating class to add a listener for the right button click.

Try running this.

5. It looks like all the old android listener code isn't running anymore after we overrided it.

It looks like that while we're adding a listener, all the complex code in the old android operating system isn't being set up, as we've overridden the initialize.
Try using the super method to fix this.

6. Extension Question: Try looking at the source code.

Source Code Link
We have developed the original application in Java. This means that while developing this program we were actually using the same techniques that you are currently learning. If you look at the source code you will see how we have implemented OOP techniques to make the program work. Don't worry if it looks daunting, your knowledge so far should be more than enough to tackle interpreting the source code.
Note, We have frequently used reflection in our application so that we can evaluate and check code - reflection is an advanced Java topic so don't worry if it doesn't make complete sense at the moment. If you choose to continue in your studies of Java, you will no doubt run into reflection again.
An important part of being an Object Oriented Programmer is being able to read other people's sourcecode. Through this question, you will learn this skill.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. Construct a class to represent the file uploader.

To build a file checker, we first need to construct the class to hold all our logic.
Using the template provided, create your own file checker. Once you are done, load it into the application and view the results.
Template Link

2. Implement a checking system to verify the inputs.

Now now, the check button doesn't do anything, as the logic hasn't been defined – in order to check the docx file, add a check method to your class, which returns true or false depending on the type.
Modify your class to check the docx files.

3. Improve your checking system to verify a larger variety of files..

It looks like we've got some more files to check. Add corresponding check functions which return true or false depending on the type.
Modify your class to use overloading to check more types of file.

4. Now override the initialization method of the operating class to add a listener for the right button click.

Notice how all this code you've written follows the same structure?
It turns out all the files with a verify method are subclasses of verifiable.
Try implementing polymorphism to make your code simpler.

Abstraction

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Encapsulation

Story

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Inheritance

Story

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Polymorphism

Story

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Episode 1: Abstractions on the mind

About this episode

As always, answers for the following questions can be found in the about section.

Practice Questions

1. Consider an application system controlling a bank, and one controlling a Game Console.

2. Consider an application to organise books in a bookstore, and an application used to manage book printing orders

3. Consider an application to manage printing documents, and an application to display documents.

Story Questions

For these questions, you will need to download the following application: Application Link

1. Using the template provided, try making your own book abstraction.

2. It looks like some customers want to specify books by more than just their titles.

3. Making an abstraction more specific is not always a good thing.

4. Extension Question: Try building your own book record.

Practice Questions

1. Given the following class diagram, try producing corresponding Java code.

2. Given the following class diagram, try producing corresponding Java code.

3. Given the following class diagram, try producing corresponding Java code.

4. Extension Question: Try rebuilding the previous classes in another Object Oriented Language such as Python.

Story Questions - Fixing the Management System

For these questions, you will need to download the following application: Application link

1. First, to fix the manager application, we'll need to reconstruct the account class.

2. Did you see that? It looks like there's another entity on the system..

3. Extension Question: Try creating your own banking system.

Practice Questions

1.From the following UML diagram of a notebook and a textbook class in a book management system, try using abstraction to extract out common functionality into a parent class.

2.From the following UML diagram of a mouse and keyboard class in a physical device management system, try using abstraction to extract out common functionality.

3. From the following UML diagram of a driver and a car in a car hire management system, try extracting out common functionality.

4. Extension Question: Try rebuilding the previous classes in another Object Oriented Language such as Python.

Story Questions

For these questions, you will need to download the following application: Application Link

1. To make a water plane, we need to first build some parts that are waterproof.

2. Construct a plane that can land on water.

3. Extension Question: Develop a system to play rock, paper, scissors.

Story Questions

For these questions, you will need to download the following application: Application Link

1.In order to make the ancient mechanism work, we'll need to re-implement it's checking methods.

2. Fix the ancient mechanism so it crushes rocks.

3. Now, it seems like all the rocks are crushed.

4. Extension Question: Try Implementing Other types of Polymorphism.

5. Extension Question: Try building a System in Python.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. What attributes you will include in your simulation?

2. Build an abstraction representing the object.

3. Improve your simulation by adding a mass attribute.

4. Improve your simulation by adding a velocity attribute.

5. Extension Question: Try building a Particle Simulator in Java.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. Construct a patient class to hold all the details about the patient.

2. Improve your model by adding symptoms for each patient.

3. It looks like there's a bug on the system - patient data is being changed.

4. Implement methods to selectively allow use of the private details.

5. Extension Question: Try creating your own version of a Patient manager system from scratch.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. Construct a class to represent the new phone system.

2. Improve your Operating System by inheriting from the base Android Operating System.

3. Some base android features don't work with the new hardware. Can we fix it?

4. Now override the initialization method of the operating class to add a listener for the right button click.

5. It looks like all the old android listener code isn't running anymore after we overrided it.

6. Extension Question: Try looking at the source code.

Theory Questions

For these questions, you will need to download the following application: Application Link

1. Construct a class to represent the file uploader.

2. Implement a checking system to verify the inputs.

3. Improve your checking system to verify a larger variety of files..

4. Now override the initialization method of the operating class to add a listener for the right button click.