LabExercise 0: Getting Started

COMP112 2020 Tri 1: Introductory Lab Exercise

  • Due 12 Mar 10am

Overview

This lab exercise introduces you to the software that you will be using for your lab assignments, gets you to run and modify a very simple Java program, and presents a programming puzzle in which you have to write instructions for a mouse in a maze. As in all the assignments, you will then write up your thinking about the "assignment" in a short file and submit it along with the other required files.

Goals

After completing this lab exercise you should:
  • Know the basics of operating a linux workstation with KDE.
  • Be able to use a browser to access course information and download the necessary files.
  • Be able to use BlueJ to read, edit, and run small Java programs.
  • Be able to use the online submission system to submit your files.
  • Be able to write a program to direct a mouse out of a maze.

To Submit

  • Modified version of NameTagPrinter.java
  • The Reflection.txt file with answers to the questions.

Summary of the lab exercise

There are eight parts in this lab exercise which you should do across your lab sessions.
  1. Registering and logging on:
    right Make sure you can log on to the lab computer systems and read the Lab rules.
  2. Driving the lab computers using KDE:
    right Make sure you can access, copy, move, and delete files.
  3. Navigating the COMP 112 web pages:
    right Make sure you can use the web browser to access information on the COMP 112 web site, including the files you need for your assignments.
  4. Using the web-based submission system:
    right Make sure you can submit your assignments for this course, by submitting NameTagPrinter.java.
  5. Running BlueJ:
    right Make sure you can run BlueJ (the Java program development environment you will use for editing and running Java programs) by running NameTagPrinter.java inside BlueJ, editing it to make the name tags different, and then submit your edited NameTagPrinter.java file.
  6. Solving a programming puzzle:
    right Run the MazeMouse program, and get the mouse out of the maze. You should work on this in pairs.
  7. Extending your java program:
    right Add some new features to NameTagPrinter.java. You should work on this in pairs.
  8. Reflecting on the programs you have worked on:
    right Complete the Reflection.txt file and submit it.

1: Registering and Logging on

In order to use the ECS lab computers, including the assignment submission system, you must have an active ECS username and password. This identifies you as an authorised user, and allows you to access your files and various files provided by the School. Note that the ECS computers are on a different system from the rest of the university, and therefore you need to set up your username and password on the ECS computers. Your username will be the same as on the other university computers, but your password should be different. Note, your username must be typed with lower case letters not capital letters. Your password can have both.

The first thing to do is to register/activate your ECS account (unless you have already done it via the web). If you are in the ECS labs, log in to your workstation using the username register and the password register. The computer will then lead you through the remainder of the registration process.

Note that any account not activated within the first three weeks of the trimester will be disabled.

Please read the lab rules carefully - it is important that you know what you can and can't do on the ECS lab computers.

Note, the computers in the ECS labs should initially be displaying a login window. If the screen is dark, it may be in power-saving mode, and moving the mouse will re-activate it. If the computer shows a desktop screen because someone else is logged in already, ask your tutor for help.

Once you have successfully activated your ECS account, you can log on, using your username and password. The login process takes some moments to run, so be patient. If your username and password do not seem to work, ask the lab tutor for help.

2: Using KDE

KDE provides a desktop environment, similar to Windows on a PC, or a Macintosh. The most important element is the "start" button go.png in the bottom left, which is like the "Start" button on Windows. Unless you have used KDE before, you should work through the Introduction to KDE tutorial. (There should be a pile of printed copies of the tutorial in the lab). If you have any questions or problems with tutorial, please ask a tutor.

For most assignments, we will provide demo programs to show you how your java programs should work. These are provided in the COMP112 folder on your desktop, and you can run them on the lab workstations. They cannot be run on your home machine (to make this possible would give away all the answers). For this lab exercise, there is an example demo program you can try out.

right Now, using the file browser, navigate to the lab0-demos folder in the COMP112 folder on your desktop, and run the TriangleDemo program by clicking on it. Note that you don't have to write this program!!

The KDE tutorial and the rest of this lab exercise only introduce the bare essentials needed to do the practical work for COMP 112. You will learn more as you become familiar with the computer system and become more confident in using it. We expect you to learn much of this by yourself by exploring the various menus, buttons, etc, by trying things out to see what they do, and by talking to tutors and other students. You might also find it useful to read this handout again in a few weeks, to remind you of what it covered.

3: Using a browser and accessing the COMP112 web site

KDE provides several web browsers, including Firefox, and Google Chrome. To start up a browser, click on the appropriate icon or use the startup menu.

When your browser first starts up, you may see a License Agreement window. If so, click on the "Accept" button. If the school's home page is not showing, get to the school home page by typing www.wgtn.ac.nz/ecs into the white box at the top of the window, and then typing return.

To access the COMP112 website, you can:
  • Type in the URL https://ecs.wgtn.ac.nz/Courses/COMP112_2020T1, OR
  • From the ECS home page, select the "Wiki" in the top left hand green menu, and then "Course Homepages" from the left-hand menu. This will bring up a page containing all the courses. Select "Home page" in the entry for COMP112. Do not google "COMP112": it will usually lead you to an older version of the course. OR
  • Navigate to the COMP112 homepage from the course pages on Blackboard, (if you are using Blackboard for your other courses.)

rightYou will need to access this page a lot so add it as a bookmark.

right Look through the course home page to see what is there.

Look at the weekly timetable, showing the times of the lectures, labs, etc; Look at the course schedule, which is where you can access copies of the slides from the lectures;

right Look at the course Forum, where you can post questions, answers, and comments about the course for other students and staff.

There is a "Help" button at the top with documentation on how to use the forum (you don't need to look at it now). Please remember that it is is a pretty public forum (visible to all staff and students in the school, and is monitored by the course organiser):
  • don't carry on private conversations via the forum;
  • be polite;
  • don't attack people;
  • don't post code for the assignments;
  • keep your postings at least somewhat related to topics in the course.

The Announcements thread on the forum is for the staff to post important announcements about the course. It is probably a good idea to get "notifications" for this thread, so that all announcements get automatically emailed to you. That way, you won't have to keep coming back to check the announcements thread (though the latest three announcements are always on the course front page).
right Click on the Announcements thread on the forum page, and then click on the "notifications" button just next to the "Add to Favorites" button (not the button at the top of the page). Activating Notification will send each announcement to your ecs email address which is forwarded to your myVUW email address (unless you have changed it).

right Look at the Assignments page and find the online version of Lab Exercise 0 (this lab exercise). Find the link near the top of the lab exercise for downloading a zip file of all the files needed for the lab exercise.

For each lab and each assignment, we will provide such a zip file.

right Download the zip file now and unpack it to your home folder.

The browser may just save the zip file. If so, you will need to open it to unpack all the files. Alternatively, the browser may automatically unpack all the files. Either way, you should end up with a folder called COMP112-2020T1-Lab0 in your home folder containing the files you need. Make sure that it contains a folder called NameTagPrinter, a folder called MazeMouse, and a file called Reflection.txt .

Note: You can do the same thing from your home computer to download the files to that computer.

To find out how to run Java and BlueJ on your laptop or home computer, look at the JavaResources page (click the JavaResources link on the left panel), and then click on the Using Java and BlueJ at home link. This has instructions for how to set things up.

4: Submitting your answers

For every assignment, when you have finished your program or programs, you should submit them using the online submission system.

right In your web browser, go to the top of the Lab Exercise 0 page, and click on the "Submit" link. It should look something like this:

submission.png

The submission page will let you upload your files to the submission system, where the tutors and markers can access them. You may re-submit the same file as often as you like, but the submission system will only remember the latest version of each file.

right Use the "+Add files..." button, then navigate to and select the NameTagPrinter.java file, (which you downloaded in the previous section). Once you have added the NameTagPrinter.java file, it should look like this:

submitted-file.png

Note
  • the green line indicates that the file was successfully added. If you click on the Submission logs button, you will also notice that your file is recorded as being uploaded.
  • the green tick next to the name NameTagPrinter.java in the Assessment Info panel shows that you have submitted one of the required files.
submission-required-files.png

If you accidentally add a file the submission system does not accept, e.g. NameTagPrinter.class, the line will turn red as in the image below:

failed-add-file.png

The error message helps you identify what the problem is.

In COMP 112 you are permitted and encouraged to work on the core and completion parts of the assignments in pairs, as long as you both include the name of the person you worked with in the files for your assignment. If you worked with someone, then you should also specify their name or username in the submission system so that it is properly recorded. Enter the name of the person you worked with in the "Details of working in pairs" section and click on the "Update" button. Note that for the information to be recorded, you must click on the "Update" button.

working-in-pairs.png

right Finally, click the "Complete submission" button to complete the submission. This will run automated checking of your submitted files that we have set for each assignment (it will also email you a receipt if the completion process is successful).

As you have not yet met all the requirements of this lab exercise (you still need to add the Reflection.txt file), you will see the following image. Note this contains instructions on how to fix the submission.

complete-missing-file.png

Even if the completion process is not successful, you can view which files have been submitted in the Submitted files section.

Once this you do part 8 of this lab exercise and submit your Reflection.txt file, your complete submission process should succeed and you will be presented with the following screen. Note how the box surrounding the "Complete submission" button has now turned green and shows the time of your completion.

successful-complete.png

5: Java and BlueJ

This section of the lab exercise will lead you through just the first steps of using BlueJ to write Java programs.

Java is the programming language you will use in the course, and BlueJ is an application that allows you to construct, run, and debug Java programs.

For this lab, we will go through the steps of using BlueJ to run a program, and make minor changes to it.

Opening a Java program with BlueJ

A Java program consists of one or more files containing Java source code; these files must have names ending in .java

BlueJ has a "project" for each program that you are working on. A BlueJ project is a folder that contains all the Java files for the program, along with any data files the program uses, the class files that the compiler creates (which is what the computer actually runs), and several other files that BlueJ creates itself. When you download the files for an assignment, any Java programs should already be organised into BlueJ projects. Check that your COMP112-2020T1-Lab0 folder contains a folder called NameTagPrinter; this is a BlueJ project.

To work on a Java program, the safest way is to start up BlueJ and then open the project for that program from inside BlueJ. You may also be able to double click on the package.bluej icon in the project folder, but this doesn't always work.

right Start up BlueJ (click the "Start" button, then select "BlueJ" from the "Development" submenu).

right Open the NameTagPrinter program from inside BlueJ using the "Open Project" option from the "Project" menu, and navigating to the NameTagPrinter folder.

This should open a window like the following:

bluej-nametagprinter.png

Editing, Compiling and Running a Java program

The NameTagPrinter program displays a name tag in two different ways. The program is very small and contains just one Java file: NameTagPrinter.java

BlueJ displays each class in the program (each class corresponds to one Java file in the project) as an orange rectangle.

If you right-click on the rectangle for a class, it will pop up a menu of actions that you can perform on the class or its file: including "Open Editor" (to read and edit the program) and "Compile" (to compile the file). If the file is compiled, then there will be additional actions.

right View the NameTagPrinter.java file using the "Open Editor" command. Note you can double click on the rectangle for the class to activate the "Open Editor" command.

It should open up a new window with the Java program code. The NameTagPrinter program has three methods, each of which have a sequence of actions. Read through them and try to guess what they will do. (The "UI" in the code refers to the user interface window where the programs will read and print text and draw shapes.)

Before a Java program can be run (or "executed"), it must first be "compiled" (ie translated) into Java byte code - a form that the computer can execute. The compiled form is stored in files with names ending in .class

If a Java file has been compiled (and is therefore ready to be run), BlueJ will show the corresponding rectangle in the project window as plain orange; if it hasn't been compiled, it will have diagonal shading on it.

right Compile the NameTagPrinter.java file, by right-clicking the NameTagPrinter rectangle and choosing Compile, or by clicking the "Compile" button on the left of the project window.

The rectangle should turn plain orange. (Check with your tutor if it doesn't).

It is possible, especially on other computers not in the ECS labs, that the ecs100 library file has not been installed. If so, BlueJ will complain that it can't find ecs100. To fix this,
  • Click on the Tools menu,
  • Select the Preferences option,
  • Click on the Libraries tab.
  • Click on the Add button
  • Navigate to the folder where you unpacked the lab 0 zip file
  • Select the ecs100.jar file (click it then click the Open button)
  • Click the OK button (which will pop up an information box)
  • Try compiling the NameTagPrinter again.

Now you can use BlueJ to run the program. To run a program in Java, you have to create the program object, so the first step is to make a new NameTagPrinter object.

right Right click on the NameTagPrinter rectangle, and choose the new NameTagPrinter() option. When it asks for the name of the instance (the object), just click "OK".

This will create a new red rectangle at the bottom of the BlueJ window representing the new NameTagPrinter object.

bluej-nametagprinter.png

right Right click on the new red rectangle at the bottom of the BlueJ window, (the NameTagPrinter object), and select one of the actions:

bluej-nametagprinter.png

right Choose the void drawNameTag() option.

right Now do it again, but choose the void printNameTag() option.

There is also another way of running this program using buttons:

right Choose the void setupGUI() option.

The program should put some buttons on the window.

right Click the buttons. Do they do what you expected?

You now know how to run a simple Java program using BlueJ.

Modifying a Java program

You should now modify the program to make it behave a bit differently. To change the program, you need to go back to the editor window with the code. If you closed it, open it again by right-clicking on the NameTagPrinter rectangle (the orange class, not the red object).

right Now modify the program so that it says "Hi I'm" on the name tag instead of "HELLO, my name is". You can change either (or both) of the printNameTag or drawNameTag methods.

right Run the methods again to check that your modifications were correct. Note that you will need to compile the program again before you can run the methods.


You now know the basics of running and editing a simple Java program using BlueJ.

right Close BlueJ.

right Submit your modified version of NameTagPrinter.java. Make sure that you submit the .java file, not the .class file: the .class file is the compiled version which the markers cannot read!

6: Solving a programming puzzle

This part of the lab exercise is optional, and only if you have time. It involves working out instructions (ie, a program) for a mouse that is trying to get out of a maze. The MazeMouse program (part of the zip file you downloaded and unpacked) will let you try out your mouse instructions. You can watch a short video of the MazeMouse program to help understand what you have to do.

right From inside BlueJ, open the MazeMouse program using the "Open Project" option from the "Project" menu, and navigating to the MazeMouse folder. (You may have to restart BlueJ if you closed it. You may also want to close the NameTagPrinter program if it is getting in the way; BlueJ is happy to have two separate programs open at once, but it tends to get confusing.)

right Run the MazeMouse program by right-clicking on the MazeMouse rectangle and choosing new MazeMouse(). Right click on the MazeMouse object and choose the void setupGUI() option.

You should now see a simple square maze with a mouse in the top left corner. You can modify the maze by clicking on squares to change walls to spaces and vice versa.

The basic actions of the mouse are to move forward (" F "), turn left (" L "), and turn right (" R "). Your program for the mouse will consist of sequences of these basic actions. For example, the sequence " FFLF " would make it take two steps forward, turn left, and take one more step forward.

The mouse is very short sighted and can only see the square ahead of it and the squares on each side. It can distinguish five different situations:
  • Space ahead: There's a blank space ahead of the mouse (it ignores what's on each side)
  • Space only on left: There's a wall ahead of the mouse, and to its right, but a blank space to its left.
  • Space only on right: There's a wall ahead of the mouse, and to its left, but a blank space to its right.
  • Space both sides: There's a wall ahead of the mouse, but blank spaces to both its left and its right.
  • At dead end: There are walls ahead of the mouse and on both sides.

You have to give the mouse a sequence of actions to perform in each situation by typing in a sequence of F 's, R 's, and/or L 's in each of the white boxes in the left hand panel. For example, you might want to make it take two steps forward when there is a space ahead, so you would type one FF in the "Space ahead" box.

You can then make the mouse follow your instructions using the "Step" or "Run" buttons.

Your goal is to find a set of instructions for the mouse that will enable it to get out of the maze, whatever the shape of the maze! You can assume that the mouse always starts in the top left corner of the maze (the "Restart" button will put the mouse back in the corner). The obvious instructions don't work, so you will have to think more carefully! Once you have some instructions that seem to work, try changing the maze to check that it still works correctly.

right Get in a group of three people to discuss your ideas for solving the puzzle. When you come up with a possible program, try it out, and try to find a way of "breaking it" - changing the maze so that it won't work. Can you get a program for the mouse that will work on any maze?

7: Extending your java program

(Optional - only if you have time)

We haven't covered very much Java in the lectures yet, but you should already be able to use the ideas from the NameTagPrinter program and the TemperatureCalculator to extend the NameTagPrinter program in several ways.

right In small groups of three, work on the following changes:
  • make it draw a larger rectangle;
  • draw the name tag as a circular button;
  • make the name tag have a coloured background;
  • make it draw two nametags (a button and a desk nameplate) next to each other;
  • make it ask for name and school, and put both on the nametag.
  • make the name tag have an image in the top left corner (you can copy an image from anywhere to get this).
  • make the name tag be the right size for the name - longer names have wider name tags (you may need to find out how many characters are in the name!)
  • make the program ask the user for the width and height of the nameplate, and draw the nameplate with a rectangle that size.
  • make the fontsize of the name be 1/4 of the height of the nameplate, (whatever height the user entered).
You may need to look up the documentation to work out how to do these things (there is a link to JavaDocumentation on the sidebar of any of the COMP 112 web pages).

8: Reflecting on the lab exercise

The most important part of the learning in this course happens while you are writing programs for the assignments. Doing programming is critical to learning about programming. But you will learn more if you also think about what you have done and put things together to to get a deeper understanding.

In each assignment, we will ask you to reflect on what you have learned while doing the programs, giving you a set of questions to lead your thinking. You should spend a little while working on answers to the questions. The questions are meant to prompt and lead your thinking; not to constrain it. If you notice things, or realise some insights that don't quite match the questions, that's great - write those thoughts down also.

The file Reflection.txt has the questions written in it to help you. You only need to write a couple of sentences for each question.

right You should type your thoughts and answers in the file and submit it along with the code. From assignment 1, these reflections are worth 10% of the assignment marks. They are not marked for "right" and "wrong", but for whether you actually thought about what you have been doing.

right Submit Reflection.txt in the same way that you submitted NameTagPrinter.java.

right Complete the submission process and check that you have received a receipt for your submission.

Afterword
There are several important links at the bottom of the course home page:
  • Support.WebHome has lots of useful documentation on many different aspects of the ECS computing system. Read through the list of topics just to get an idea of what is there - you may need some of it later.
  • Change password, lets you change your password on the ECS computer systems (which are also needed for accessing the forum and the submission system from home).
  • Read the advice about password security and phishing.