COMP2511 Assignment: Back in Blackout
Due: Friday, 8th of October, Week 4 at 5pm.
Value: 15% of course mark
Contents
COMP2511 Assignment: Back in Blackout
Contents
0. Change Log
Your Private Repository
Introduction Video
1. Aims
2. Preamble and Problem
A simple example
Simulation
3. Requirements
!
Assumptions
Devices
”
Files
#
Satellites
$
Visualisation
%
4. Program Structure
5. Tasks
Task 1 – Modelling – 6 marks
&
Task 1 a) Create Device
Task 1 b) Remove Device
Task 1 c) Create Satellite
Task 1 d) Remove Satellite
Task 1 e) List all device ids
Task 1 f) List all satellite ids
Task 1 g) Add file to device
Task 1 h) Get device/satellite information
Task 1 Example
Task 2 – Simulation
‘
– 9 marks
Task 2 a) Run the Simulation
Task 2 b) List all entities in range
Task 2 c) File Transferring
Task 2 Example
Task 3 (Extra Devices/Satellites) – 5 marks
(
Task 3 a) ElephantSatellite – 3 marks
Task 3 b) CloudStorageDevice – 2 marks
6. Other Requirements
)
7. Design
*
8. Testing and Dryruns
+
9. Style and Documentation
,
10. Tips
–
11. Submission
.
12. Late Penalties
13. Marking Criteria
✅
14. Credits
0
0. Change Log
0. Change Log
Mon 20th Sept 12-3pm. Some minor clarifications to wording
Mon 20th Sept 6-9pm. Clarifications, Elephant properties were missing, all velocities set to per minute instead of
per hour.
Mon 20th Sept 12am. Release Student Repos
Tue 21st Sept 12pm. Release Sample Implementation
Tue 21st Sept 8pm. Clarify Shrinking Satellite Behaviour
Sat 25th Sept 4pm. Rephrased some relay logic to make it clearer
Sat 25th Sept 9pm. Fixed up Simple Example since calculation result was wrong (18 + 128 != 136 it’s equal to 146…)
Sun 26th Sept 4pm. Clarified Relay behaviour with Desktops/Standard satellites (and other ‘requirements’)
Tue 28th Sept 5:30am. Clarified Shrinking Satellite
Mon 4th Oct 4pm. Clarified that communicable satellites includes relay satellites (and their communicable satellites)
Your Private Repository
Is located at https://gitlab.cse.unsw.edu.au/COMP2511/21T3/students/z555555/assignment
Make sure to replace the zID in the header.
Introduction Video
You can watch an introduction video here https://thebox.unsw.edu.au/3CF51850-1B4D-11EC-9F0B728F51087198
1. Aims
Practice applying a systematic approach to object-oriented design process
Gain experience in implementing an object-oriented program with multiple interacting classes
Gain hands on experience with Java libraries
2. Preamble and Problem
So much of today’s technology uses Global Positioning System (GPS) information. For example, tagging photographs
with their location, guiding drivers with car navigation systems, and even missile control systems. There are currently 31
active GPS satellites (as of the time of writing this) orbiting the Earth all together providing near-constant GPS coverage.
In the far future, society has become advanced to the point where they have begun to occupy a series of moons and
asteroids around the planet Jupiter. Individuals rely on satellites for all their communication desires. Three major
satellites exist around Jupiter.
This assessment aims to provide you with design experience for a non-trivial system. You will be architecting and
modelling how these multiple satellites will communicate and function with various devices. The form of communication
that you will be simulating is a simplified version of the modern internet, simply just file transfer. You can either upload a
file to a satellite from a device, download a file from a satellite to a device, or send a file from a satellite to a satellite.
Your solution should adopt an Object-Oriented approach that utilises concepts such as abstraction, encapsulation,
composition, and inheritance, as taught in lectures.
A simple example
Let’s assume initially there is a Standard Satellite at height approximately 80,000km above the centre of Jupiter and
at θ = 128 degrees (anticlockwise). In addition there are 3 devices; DeviceA, DeviceB, and DeviceC. DeviceA and DeviceC
are handheld devices, whereas DeviceB is a desktop device.
https://gitlab.cse.unsw.edu.au/COMP2511/21T3/students/z555555/assignment
https://thebox.unsw.edu.au/3CF51850-1B4D-11EC-9F0B728F51087198
In this system, the satellite can talk to device A and device A can talk to the satellite (communication is done by sending
files) since they are in range of each other. SatelliteA however cannot talk to DeviceB (and DeviceB cannot talk to
SatelliteA) because Standard Satellite s have restrictions on what devices they can talk to (discussed in more detail
later). Finally SatelliteA cannot connect to DeviceC because it’s not in visible sight range. The red line in the image
highlights this.
Devices are static and will not move, but satellites can! Satellites move based on a constant linear velocity, in this case
Standard Satellites have a linear velocity of 2,500 km per minute (or 2,500,000 metres). From this, we can calculate its
angular velocity based on its height (which is the radius from the center of Jupiter). For example, after 10 minutes it
would have moved a total of 2,500 / 80,000 * 10 mins = 0.03125 * 10 = 0.3125 radians ~= 18 degrees (note
that we don’t have to account for the fact they are measured in km here since the extra 10^3 component will cancel
out). This means our new position is 18 + 128 which is approximately 145-146 degrees .
Eventually after moving for a couple more minutes it will get out of range of the devices A and B.
Secondly, we need to look at interaction between satellites and devices. They can communicate through the transfer of
files. Files can be transferred between satellites/devices and other satellites (files can not be directly sent from device to
device).
To begin let’s create a new file on a device. Clicking on DeviceA and pressing Create File as shown below we can create a
file.
Once created files can’t be modified/deleted, furthermore every filename has to be unique. Creating a file called Hello
World! with it’s content also being Hello World! we can view it by going to the device again and clicking Open File as
shown below.
We can then send this file to our satellite by just clicking on the device ensuring the file and satellite are selected as
below then clicking Send File .
ℹ
NOTE: This problem will not require any heavy use of mathematics, you will be provided with a library
that will perform all the calculations for you.
If we then try to open the file on the satellite we notice that it is empty and says 0/12 for its size. This is because files
transfers aren’t instant, they are based on the bandwidth of the satellite. Standard Satellites are relatively slow, so they
will take 12 minutes to send this file since they only send at 1 byte per minute. If we let it run for at least 12 minutes and
look again we will see the file has finished sending.
We could then continue this by running the simulation a little longer and letting the satellite orbit around to DeviceC and
then sending the file down to DeviceC.
Simulation
A simulation is an incremental process starting with an initial world state, say WorldState_00. We add a specified time
interval of 1 minute and calculate the new positions of all the satellites after the minute. We then go and update all the
connections accordingly to derive the next world state WorldState_01. Similarly, we derive WorldState_02 from
WorldState_01, WorldState_03 from WorldState_02, and so on. This act of feeding a world state into the next forms a sort
of state machine. An similar example of this is Conway’s Game of Life.
WorldState_00 -> WorldState_01 -> WorldState_02 -> …
In our case our simulation runs at an accuracy of 1 minute and each state transition will take only 1 minute.
3. Requirements
!
https://playgameoflife.com/
There are three tasks set out for you.
1. Model the problem, including:
Modelling the satellites/devices.
Satellites/Devices must be able to be added/removed at runtime (with various consequences)
Most importantly a series of ‘queries’ about the current world state such as what devices currently exist.
2. Allow satellites/devices to send files to other satellites.
3. Implement a special device and a special satellite with unique properties.
Assumptions
In this problem, we are going to have to make some assumptions. Let us assume that:
Satellites move around at a constant linear velocity regardless of their distance from the planet (their angular
velocity would change based upon the distance, though).
The model is two dimensional
Objects do not rotate on their axis and simple planatary orbit is the only ‘rotation’ that is allowed in the system.
Jupiter has a radius of 69,911 kilometres.
For the sake of consistency:
All distances are in kilometres ( 1 km = 1,000 m ).
Angular velocity is in radians per minute (not per second).
Linear velocity is in kilometres per minute (not per second).
Devices
”
There are three types of devices available. Each device has a maximum range from which it can connect to satellites.
HandheldDevice – phones, GPS devices, tablets.
Handhelds have a range of only 50,000 kilometres (50,000,000 metres)
LaptopDevice – laptop computers.
Laptops have a range of only 100,000 kilometres (100,000,000 metres)
DesktopDevice – desktop computers and servers.
Desktops have a range of only 200,000 kilometres (200,000,000 metres)
Files
#
Devices can store an infinite number of files and can upload/download files from satellites. Files are represented simply
by just a string representing their content and a filename representing their name.
All files can be presumed to purely consist of alphanumeric characters or spaces (i.e. a-z, A-Z, 0-9, or spaces) and
filenames can be presumed to be unique (i.e. if two files have the same filename they will have the same content).
Furthermore, since we are dealing with such a simple subset, 1 character is equivalent to 1 byte. We will often refer to
the size of files in terms of bytes, and the file size only relates to the content of the file (and not the filename).
To send files the target needs to be within the range of the source BUT the source does not have to be within the range
of the target. For example if a HandheldDevice (range 3,000 km ) is 4,000 km away from a StandardSatellite
(range 15,000 km ) it can’t send files to the satellite but it can receive files from the satellite. If the device is 16,000 km
away from the satellite neither can interact with each other. Satellites can also send files to other satellites but devices
can not send files to other devices.
Files do not send instantly however, and are limited by the bandwidth of the satellites. Satellites will always ensure
fairness and will evenly allocate bandwidth to all currently uploading files (for example, if a satellite has a bandwidth of
10 bytes per minute and 3 files, every file will get 3 bytes per minute. You’ll have 1 unused byte of bandwidth). You can’t
transfer a partially uploaded file from a satellite. Devices aren’t limited on the number of downloads/uploads they can
do.
If a device goes out of range of a satellite during the transfer of a file (either way) the partially downloaded file should be
removed from the recipient. This does raise the question of whether or not you should start transferring a file if it’s
obvious that it won’t finish. Solving this problem is mostly algorithmic and isn’t particularly interesting to the point of this
assignment so you don’t have to do anything special here: if someone asks to transfer a file… begin to transfer it.
Satellites
$
There are 2 specialised types of satellites (and one basic one). Satellites have a set amount of bandwidth for transferring
files and a set amount of storage.
Default direction for all satellites is positive.
StandardSatellite
Moves at a linear speed of 2,500 kilometres (2,500,000 metres) per minute
Supports handhelds and laptops only (along with other satellites)
Maximum range of 150,000 kilometres (150,000,000 metres)
Can store up to either 3 files or 80 bytes (whichever is smallest for the current situation).
Can receive 1 byte per minute and can send 1 byte per minute meaning it can only transfer 1 file at a time.
ShrinkingSatellite
Moves at a linear velocity of 1,000 kilometres (1,000,000 metres) per minute
Supports all devices
Maximum range of 200,000 kilometres (200,000,000 metres)
Can receive 15 bytes per minute and can send 10 bytes per minute.
Can store up to 150 bytes and as many files as fits into that space.
Has a ‘quantum compressor’ meaning all files stored on the satellite that contain the phrase “quantum” only
take up two-thirds (2/3) of their original size.
Lowercase quantum is fine, you don’t need to worry about any casing here, no need for case insensitivity,
and the file simply just has to contain “quantum” anywhere
This sort of compression means that the ‘data’ only takes up 2/3 of it’s original size but when
sending/receiving the file it still has to receive and send the full payload
For example the message quantum is 7 bytes but compressed is 5 bytes. Thus when sending it, it
needs to send 7 bytes and when receiving it, it would need to receive 7 bytes.
Hint: You aren’t actually doing any compression here, you can just keep/store the strings as they currently
are and treat the compression as a representation of what their fully transferred ‘size’ is.
RelaySatellite
Moves at a linear velocity of 1,500 kilometres (1,500,000 metres) per minute
Supports all devices
Max range of 300,000 kilometres (300,000,000 metres)
Cannot store any files and has no bandwidth limits
Devices/Satellites cannot transfer files directly to a relay but instead a relay can be automatically used by
satellites/devices to send to their real target.
For example if a HandheldDevice (range 50,000km ) is 200km away from a StandardSatellite that it
ℹ
To save you some googling v = r * ω (where v is linear velocity i.e. metres per minute, ω is angular
velocity i.e. radians per minute, and r is the radius / height of the satellite).
wishes to communicate with, it is able to communicate to the satellite through the use of the relay if the
relay is within 50,000km of the device and the satellite is within 300,000km (the range of the relay) of the
relay.
Files being transferred through a relay should not show up in the relay’s list of files.
Only travels in the region between 140° and 190°
When it reaches one side of the region its direction reverses and it travels in the opposite direction.
This ‘correction’ will only apply on the next minute. This means that it can briefly exceed this
boundary. There is a unit test that details this behaviour quite well called
testRelaySatelliteMovement in Task2ExampleTests.java
You can either do the radian maths here yourself or use the functions in src/unsw/utils/Angle.java
to do comparisons.
In the case that the satellite doesn’t start in the region [140°, 190°] , it should choose whatever direction
gets it to the region [140°, 190°] in the shortest amount of time. As a hint (and to prevent you having to
do math) this ‘threshold’ angle is 345° .
If a relay satellite starts on the threshold 345° it should take the positive direction.
Relay satellites don’t allow you to ignore satellite requirements (other than visibility/range), for example
you can’t send a file from a Desktop Device to a Standard Satellite due to the fact that a Standard Satellite
doesn’t support Desktops. This should hold EVEN if a Relay is used along the way. (Since this was a late
clarification it will NOT be tested by any marking tests).
HINT: because there are no bandwidth limits and you don’t have to show any tracking of files that go through
the relay. Keep it simple! Don’t over-engineer a solution for this one. You’ll notice that the frontend when
drawing connections that utilise relays don’t go through the relay as shown below.
⚠
As with any software, bugs could exist in either the frontend or the reference implementation. Thus
you should treat the specification as the final word and not the reference implementation. If you do notice
any bugs or issues, please raise it on the forum so it can get fixed (or a workaround will be provided).
Furthermore as the frontend expects that most of the code follows the specification you may run into weird
bugs if you have wildly different behaviour.
File Path Description
Should
you
need
to
modify
this?
BlackoutController.java src/unsw/blackout/BlackoutController.java
Contains one
method for each
command you
need to
implement.
Yes.
App.java src/App.java
Runs a server for
blackout.
No.
MathsHelper.java src/unsw/utils/MathsHelper.java
Contains all the
math logic that
you’ll require.
No.
Contains an
abstraction for
Visualisation
%
To help you understand this problem we’ve made a frontend for the application you are writing, we also have a
reference implementation for you to refer to. You’ll also find that the starter code will have a simple webserver to run
this frontend for you (already written) such that you can run the UI locally.
https://blackout21t3.azurewebsites.net/
This is NOT necessary for you to get marks, and it is more there just for those that enjoy seeing something slowly come
together as they complete tasks. It’s possible and still quite nice to just use the reference implementation + JUnit tests to
design and build your solution without ever having to run and test the UI locally.
Functionality is listed below;
You can click on a satellite or a device to view it’s properties, as well as all the files it currently has, send files to
other satellites, create files if it’s a device, or delete the entity
You can mouse over any satellite/device to see all the possible targets
You can click on anything near the radius of Jupiter to create a device and anywhere else in space to create a
satellite
There are buttons on the top left to refresh the screen (for whatever reason) as well as run simulations for set
periods of time
If your backend throws any exceptions an error will popup in the UI and an error log will be in the Java output window in
VSCode (exception transferring file tasks which require the throwing of certain exceptions).
4. Program Structure
https://blackout21t3.azurewebsites.net/
Angle.java src/unsw/utils/Angle.java
angles that lets
you easily convert
between
radians/degrees
without having to
worry about what
‘state’ it is
currently in.
No.
ZippedFileUtils.java src/unsw/utils/ZippedFileUtils.java
Allows you to
zip/unzip strings,
useful only for
Task 3b)
No.
EntityInfoResponse.java
and
FileInfoResponse.java
src/unsw/response/models/EntityInfoResponse.java
and
src/unsw/response/models/FileInfoResponse.java
Contains the result
for certain
functions in
BlackoutController.
No.
Scintilla.java and
auxiliary files;
Environment.java,
PlatformUtils.java, and
WebServer.java
src/scintilla
Contains a small
custom built
wrapper around
Spark-Java for
running a web
server. When run it
automatically
opens a web
browser.
No.
Task1ExampleTests.java src/test/Task1ExampleTests.java
Contains a simple
test to get you
started with Task
1.
Yes,
feel
free to
add
more
tests
here or
just
create
a new
testing
file.
Task2ExampleTests.java src/test/Task2ExampleTests.java
Contains a simple
test to get you
started with Task
2.
Yes,
feel
free to
add
more
tests
here or
just
create
a new
testing
file.
5. Tasks
Task 1 – Modelling – 6 marks
&
This task is mainly focused on design, if you start with an initial design via a UML Diagram, you’ll find this will be
quite straightforward! Very little logic exists in this first task.
All methods below exist in the class src/unsw/blackout/BlackoutController.java
Task 1 a) Create Device
Adds a device to the ring at the position specified, the position is measured as an angle relative to the x-axis, rotating
anti-clockwise.
Task 1 b) Remove Device
Removes a device (specified by id). You don’t need to cancel all current downloads/uploads (relevant for Task 2).
Task 1 c) Create Satellite
Creates a satellite at a given height (measured from centre of Jupiter) at a given angle.
Task 1 d) Remove Satellite
Removes a satellite from orbit. You don’t need to cancel all current downloads/uploads (relevant for Task 2).
Task 1 e) List all device ids
Lists all the device ids that currently exist.
Task 1 f) List all satellite ids
Lists all the satellite ids that currently exist.
public void createDevice(String deviceId, String type, Angle position);1
public void removeDevice(String deviceId);1
public void createSatellite(String satelliteId, String type, double height, Angle position);1
public void removeSatellite(String satelliteId);1
public List
public List
ℹ
NOTE: id s are unique, so no 2 devices and/or satellites can have the same id.
ℹ
NOTE: final for classes means it can’t have subclasses, final for functions means they can’t have
overrides, and final for members means they can’t be modified after the constructor. You don’t have to use
it in the assignment.
3
Map<..> is similar to Dictionaries in Python and acts as a mapping between a key and a value. You can
find more information here
Task 1 g) Add file to device
Adds a file to a device (not a satellite). Files are added instantly.
Task 1 h) Get device/satellite information
Get detailed information about a single device or a satellite.
EntityInfoResponse is a struct that is supplied that contains the following members (it also comes with a constructor
and a getter).
public void addFileToDevice(String deviceId, String filename, String content);1
public EntityInfoResponse getInfo(String id);1
public final class EntityInfoResponse {
/**
* The unique ID of the device.
**/
private final String id;
/**
* The angular position of the entity in radians
**/
private final Angle position;
/**
* The height of the entity measured in kilometres
* devices will have a height equal to the radius of Jupiter.
*/
private final double height;
/**
* the type of the entity i.e. DesktopDevice, ShrinkingSatellite, …
**/
private final String type;
/**
* A map of all the files that this entity has access to.
**/
private final Map
}
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https://docs.oracle.com/javase/8/docs/api/java/util/Map.html
ℹ
NOTE: To help with testing a simulate(int numberOfMinutes) has already been written which just calls
simulate() numberOfMinutes ‘ times
Task 1 Example
You can test your implementations for Task 1 using the simple test provided in the file
src/test/Task1ExampleTests.java . Later you need to add more tests to properly test your implementations.
The method testExample uses a JUnit test to test a few world states. Please read the method testExample .
Task 2 – Simulation
‘
– 9 marks
The second tasks involves the actual simulating of the movement of satellites and transferring files.
Task 2 a) Run the Simulation
This should run the simulation for a single minute. This will include moving satellites around and later on transferring
files between satellites and devices.
@Test
public void testExample() {
// Task 1
// Example from the specification
BlackoutController controller = new BlackoutController();
// Creates 1 satellite and 3 devices
// 2 devices are in view of the satellite
// 1 device is out of view of the satellite
controller.createSatellite(“Satellite1”, “StandardSatellite”, 100 + RadiusOfJupiter,
Angle.fromDegrees(340));
controller.createDevice(“DeviceA”, “HandheldDevice”, Angle.fromDegrees(30));
controller.createDevice(“DeviceB”, “LaptopDevice”, Angle.fromDegrees(180));
controller.createDevice(“DeviceC”, “DesktopDevice”, Angle.fromDegrees(330));
// verify properties and that the devices/satellite was created correctly
assertListAreEqualIgnoringOrder(Arrays.asList(“Satellite1”),
controller.listSatelliteIds());
assertListAreEqualIgnoringOrder(Arrays.asList(“DeviceA”, “DeviceB”, “DeviceC”),
controller.listDeviceIds());
assertEquals(new EntityInfoResponse(“Satellite1”, Math.toRadians(340), 100 +
RadiusOfJupiter, “DesktopDevice”), controller.getInfo(“Satellite1”));
assertEquals(new EntityInfoResponse(“DeviceA”, Math.toRadians(30), RadiusOfJupiter,
“HandheldDevice”), controller.getInfo(“DeviceA”));
assertEquals(new EntityInfoResponse(“DeviceB”, Math.toRadians(180), RadiusOfJupiter,
“LaptopDevice”), controller.getInfo(“DeviceB”));
assertEquals(new EntityInfoResponse(“DeviceC”, Math.toRadians(330), RadiusOfJupiter,
“DesktopDevice”), controller.getInfo(“DeviceC”));
}
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public void simulate();1
3
Checkout src/unsw/blackout/utils/MathHelper there are some very useful functions there that do the
vast majority of the work for you, you shouldn’t need to figure out any complicated maths.
ℹ
This is useful for 2c.
Task 2 b) List all entities in range
Lists every entity in range of the specified entity that can communicate. Devices can only communicate with certain
satellites (as specified in the Satellites section). Satellites can communicate with every satellite and a certain subset of
devices (once again as discussed in the Satellites section).
For an entity to be in range it also has to be visible to the other entities (i.e. if you drew a line between the two entities
that line cannot go through Jupiter). This includes devices/satellites reachable due to relay satellites.
Task 2 c) File Transferring
Devices/Satellites can communicate by transferring files between each other. Files transfer progress can be measured by
looking at getInfo(String id) which contains a map of all files currently transferred/being transferred with the
current progress being (double)data.length() / fileSize * 100 . You can only transfer files to entities in range.
This function should throw an exception in the following cases (the message is important and will be marked), all of
these Exception classes should derive from the exception class FileTransferException and are provided for you.
File doesn’t exist on fromId or it’s a partial file (hasn’t finished transferring): should throw
unsw.blackout.VirtualFileNotFoundException with message equal to the file name
File already exists on targetId or is currently downloading to the target: should throw
unsw.blackout.VirtualFileAlreadyExistsException with message equal to the file name
Satellite Bandwidth is full: should throw unsw.blackout.VirtualFileNoBandwidthException with message equal
to whatever satellite has too little bandwidth
i.e. if you have a bandwidth of 8 bytes per minute and are currently uploading/download 8 files, you cannot
upload/download any more files.
No room on the satellite: should throw unsw.blackout.VirtualFileNoStorageSpaceException with message
equal to Max Files Reached if the lack of room was due to a max file cap (for example standard satellites can only
store 3 files) or Max Storage Reached if the lack of room was due to a max storage cap (for example standard
satellites can only store 80 bytes).
You’ll find all the exception classes in once place src/unsw/blackout/FileTransferException.java , exceptions are a
great case for a static nested class; for the sake of this assignment this is not a detail you need to worry/care about, just
use them as you normally would. For example throw new
FileTransferException.VirtualFileNoBandwidthException(“Satellite1”) .
Note: you don’t have to throw an exception for the case that the entity is out of range/not visible since you can presume
that all entities will be in range for at least the first minute.
public List
public void sendFile(String fileName, String fromId, String toId) throws FileTransferException;1
ℹ
We won’t give you any very malicious test cases where this will make a difference but just for
consistency; you should do the movement of satellites before you handle any download/upload for that
simulation minute.
Task 2 Example
You can test your implementations for Task 2 using the simple test provided in the file
src/test/Task2ExampleTests.java . Later, you will need to add more tests to properly test your implementation. For
Task 2 we supply a few different tests just to help you test a variety of cases.
Task 3 (Extra Devices/Satellites) – 5 marks
(
This task is intentionally meant to be difficult (intended for students aiming to achieve a High Distinction) and will test
the quality of your design in Tasks 1 and 2.
@Test
public void testExample() {
// Task 2
// Example from the specification
BlackoutController controller = new BlackoutController();
// Creates 1 satellite and 2 devices
// Gets a device to send a file to a satellites and gets another device to download it.
// StandardSatellites are slow and transfer 1 byte per minute.
controller.createSatellite(“Satellite1”, “StandardSatellite”, 100 + RadiusOfJupiter,
Angle.fromDegrees(340));
controller.createDevice(“DeviceB”, “LaptopDevice”, Angle.fromDegrees(310));
controller.createDevice(“DeviceC”, “DesktopDevice”, Angle.fromDegrees(320));
String msg = “Hello World!”;
controller.addFileToDevice(“DeviceC”, “FileAlpha”, “Hello World!”);
controller.sendFile(“FileAlpha”, “DeviceC”, “Satellite1”);
assertEquals(new FileInfoResponse(“FileAlpha”, “”, msg.length(), false),
controller.getInfo(“Satellite1”).getFiles().get(“FileAlpha”));
controller.simulate(msg.length());
assertEquals(new FileInfoResponse(“FileAlpha”, “Hello World!”, msg.length(), true),
controller.getInfo(“Satellite1”).getFiles().get(“FileAlpha”));
controller.sendFile(“FileAlpha”, “Satellite1”, “DeviceB”);
assertEquals(new FileInfoResponse(“FileAlpha”, “”, msg.length(), false),
controller.getInfo(“DeviceB”).getFiles().get(“FileAlpha”));
controller.simulate(msg.length());
assertEquals(new FileInfoResponse(“FileAlpha”, “Hello World!”, msg.length(), true),
controller.getInfo(“DeviceB”).getFiles().get(“FileAlpha”));
// Hints for further testing:
// – What about checking about the progress of the message half way through?
// – Device/s get out of range of satellite
// … and so on.
}
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ℹ
You don’t need to do all of above to get the marks for this section and your solution doesn’t have to be
perfect, make sure to incorporate your thought process in the rationale.md file.
Task 3 a) ElephantSatellite – 3 marks
ElephantSatellites have the following properties;
Moves at a linear speed of 2,500 kilometres (2,500,000 metres) per minute
Supports Desktops and Laptops only (along with other satellites)
Maximum range of 400,000 kilometres (400,000,000 metres)
Can store up to 90 bytes
Can receive 20 byte per minute and can send 20 byte per minute
When this satellite goes out of range of a device/satellite that is uploading a file, the ElephantSatellite doesn’t delete the
file but rather marks the file as transient, in which case it will continue the download from where it left off if the same
device/satellite enters range again (and the device/satellite isn’t currently transferring a file). Elephant satellites don’t
effect transfers from the elephant satellite (unless it’s to another elephant satellite).
However, it’s not going to hold it forever; if at any point memory becomes an issue (i.e. there is not enough space for
new transfers) it will delete transient files (that aren’t currently transferring) to make room.
What files you delete are up to you and you’ll be awarded subjective marks based on the design you choose here. This is
only worth 3 marks and is more intended for students who are interested in this sort of optimisation problem, a brute
force solution that just deletes the largest transient files until there is space will obtain 1.5/3 of the marks here.
Remember that files take up space equal to their maximum size, not their currently downloaded size (to prevent issues
where you can’t finish a transfer that you started).
A more complex solution could incorporate ideas such as;
Transient files take up only as much space as their data, since you can always delete them to make room.
If a file no longer becomes transient it should make sure it has enough space to download before it attempts
to continue though.
You could attempt to delete transient files from devices/satellites that are further away since they’ll take longer to
reach.
File names are unique so you could attempt to download the file from a different device/satellite.
Task 3 b) CloudStorageDevice – 2 marks
This device acts like a desktop but it auto zips files that are stored on it resulting in their file size being smaller than their
actual size.
Zipped files remain zipped while on satellites but should automatically unzip once transferred to a device that isn’t a
CloudStorageDevice (i.e. a HandheldDevice , LaptopDevice , or DesktopDevice ). This means they need less storage
space on satellites but will require the full storage space of the original file on any target device (that isn’t a
CloudStorageDevice ). The order that this happens is very important! Unzipping/Zipping should only happen after the
file has been transferred not during. That is if you transfer a zipped file of size 80 bytes (with unzipped being 120 bytes)
to a device it’ll transfer 80 bytes to the device and then once the 80 bytes have been transferred it’ll unzip that same
minute and you’ll end up with 120 bytes.
The video details this well, so I recommend you watch that if you don’t understand this.
You can use the functions ZippedFileUtils.ZipFile() and ZippedFileUtils.UnZipFile() to zip/unzip a file to
shrink/expand it.
ℹ
The reason why smaller amounts of text don’t compress well is due to the fact that compression has
overhead and for small amounts of text this overhead is quite high.
These commands zip files to a base64 encoded string (just for ease of use). Zipping small amounts of text is almost
never worth it, so you won’t see a difference (it’ll actually be slower) for small amounts of text. For example the text
“Hello World!” zipped goes from 12 to 32 bytes but the text “Hello World!” * 100 goes from 1200 to 43 bytes.
For this reason, if the zipped text is larger than the unzipped version it should send the unzipped version. A helpful hint
is that unzipFile is nice in the way that if try to unzip a normal string i.e. unzipFile(“Hello World”) then it’ll just
return the string rather than throwing an exception.
6. Other Requirements
)
You do not need to account for invalid input of any sort (e.g. device/satellite names with spaces, negative
heights) and thus do NOT need to check for any invalid input.
We will never give you two satellites/devices with the same ID.
When dealing with degrees vs radians don’t just convert all degrees to radians by hand and then manually put
inprecise doubles as constants. Good design is able to cope with varying units to maintain precision. You’ll lose
design/style marks for just hardcoding the conversions.
Most angles are given as radians.
All device ids are alphanumeric i.e. they consist of just alphabet characters and digits i.e. A-Z , a-z , 0-9 , or .
All floating point (double) values only have to be accurate to a precision of 0.01. i.e. 3.33 and 3.34 are both
‘equal’ in any test we’ll be running. You do NOT need to worry about rounding/formatting them in your code. We’ll
design test cases such that floating point accuracy issues aren’t a problem.
All satellites travel anti-clockwise (exception being Relay Satellites which can travel in both directions) angles are
measured from the x-axis, so this means their angle should ‘increase’ over time.
You should ONLY refer to positions in the range [0, 360) that is any value that is any value >= 360 should
be wrapped back around i.e. 360 = 0, 361 = 1, 390 = 30, 720 = 0, …
You may use any of the following Java libraries:
java.io
java.lang
java.math
java.net
java.nio
java.rmi
java.security
java.text
java.time
java.util
org.junit.jupiter (for tests only)
Most likely however quite a few of these libraries you’ll never use. You may not use any libraries other than these in your
assignment.
7. Design
*
You will need to identify entities, attributes and functions within the problem domain and articulate them in a UML class
diagram. The UML diagram will need to contain all key elements, including fields, methods, getters and setters,
constructors for each entity, inheritance, aggregation and composition relationships and cardinalities.
As you design your solution, you will have to make a series of design decisions based on Design Principles and Object-
Oriented Programming concepts taught in the course. Document all of your key decisions and the reasoning behind
them inside rationale.md . This can include your thought processes and internal reasoning, advice from your
tutor/forum on design decisions and course content (lectures, tutorials, labs).
Put your design in a file named design.pdf in the root directory of this repository.
Your UML Diagram and rationale will be used in the assessment of your design.
Good tools to draw UMLs are lucid or draw.io. Both of these can export to pdf.
8. Testing and Dryruns
+
The example use cases of Tasks 1 and 2 are set up to run against your code in the src/test directory and are the
dryrun for this assignment. Some more sample test cases may be released later for Task 3.
You will need to write your own additional tests.
9. Style and Documentation
,
You will be assessed on your code style. Examples of things to focus on include:
Correct casing of variable, function and class names;
Meaningful variable and function names;
Readability of code and use of whitespace; and
Modularisation and use of helper functions where needed.
Functions in your classes which are more than simple getters, setters and constructors should be appropriately
documented with Javadoc.
10. Tips
–
1. This problem is designed to require inheritance, (more so as the tasks go on). So don’t try to avoid it.
2. You should NOT store any response objects (i.e. FileInfoResponse or EntityInfoResponse) in your classes, pull the
information out of those into ArrayLists/Fields/Classes. You can create it them in the classes though.
3. Task 3 is a test of how strong your design is, if you start writing a lot of specific class code in Blackout or similar
classes (rather than pushing logic ‘into’ classes) it is probably an indication that you can cleanup some aspects of
your design.
11. Submission
.
To submit, run the command:
This requires a UML diagram called design.pdf to be in the assignment directory (top level). Good tools to draw UMLs
are lucid or draw.io. Both of these can export to pdf. It also requires rationale.md .
Run the above command in cse and then it runs the two sample tests given. Feel free to submit as you go.
You do NOT need to copy any code across to the CSE servers to submit. Just push your changes to the gitlab, then simply
run that submit command via ssh or vlab (or something else connected to cse).
12. Late Penalties
There is a late penalty of 10% per day. The penalty is applied to the maximum mark (ceiling) you can obtain.
$ 2511 submit blackout1
https://lucid.app/
https://draw.io/
https://lucid.app/
https://draw.io/
Criteria Description
No.
Marks
Correctness
– Task 1
Your code will be run against a series of autotests to determine the correctness of your
solution. You do not need to have completed Tasks 2/3 to receive full marks for Task 1.
6
marks
Correctness
– Task 2
Your code will be run against a series of autotests to determine the correctness of your
solution. You do not need to have completed Task 3 to receive full marks for Task 2.
9
marks
Correctness
– Task 3
Your code will be run against a series of autotests to determine the correctness of your
solution.
5
marks
Design
Quality
Your Object Oriented Design and UML diagram will be handmarked on the use of OO
principles, abstraction and overall cohesion.
16
marks
Code
Quality
Your code quality and style will be handmarked. This includes, but is not limited to:
2
marks
Testing Your tests will be assessed on their design and covering a range of possible cases.
2
marks
TOTAL
40
marks
You must submit by Friday 5pm, Week 5 or you will receive 0 for this assignment.
13. Marking Criteria
✅
This assignment is out of 40 marks and is worth 15% of your grade.
Commenting of code with Javadoc
Meaningful class, function and variable names
General neatness of code
Use of helper functions and external libraries
14. Credits
0
The inspiration for this assignment is derived from a problem “GPS Blackout” sourced from NCSS Challenge (Advanced),
2016. Outside of purely superficial comparisons, the problems are completely distinct.
COMP2511 Assignment: Back in Blackout
Contents
0. Change Log
Your Private Repository
Introduction Video
1. Aims
2. Preamble and Problem
A simple example
Simulation
3. Requirements 🪐
Assumptions
Devices 🖨️
Files 📨
Satellites 🛰️
Visualisation 🎨
4. Program Structure
5. Tasks
Task 1 – Modelling – 6 marks 🌎
Task 1 a) Create Device
Task 1 b) Remove Device
Task 1 c) Create Satellite
Task 1 d) Remove Satellite
Task 1 e) List all device ids
Task 1 f) List all satellite ids
Task 1 g) Add file to device
Task 1 h) Get device/satellite information
Task 1 Example
Task 2 – Simulation 📡 – 9 marks
Task 2 a) Run the Simulation
Task 2 b) List all entities in range
Task 2 c) File Transferring
Task 2 Example
Task 3 (Extra Devices/Satellites) – 5 marks 📱
Task 3 a) ElephantSatellite – 3 marks
Task 3 b) CloudStorageDevice – 2 marks
6. Other Requirements 🔭
7. Design 🏛️
8. Testing and Dryruns 🧪
9. Style and Documentation 🖌️
10. Tips 💡
11. Submission 🧳
12. Late Penalties
13. Marking Criteria ✅
14. Credits 🎥