Create a Zoo in Java, following the instructions step by step, and using the code provided.

INSTRUCTIONS TO CANDIDATES

ANSWER ALL QUESTIONS

Basic: Building a zoo

The first task is to model a zoo based on the following description.

A zoo consists of multiple areas, each of which can be identified by a unique ID. There must be exactly one entrance area, which always has an ID of zero. Any number of picnic areas and animal habitats may be added to (or removed from) the zoo. Aquariums can accommodate seals, sharks and starfish, while lions, gazelles and zebra are kept in enclosures. Buzzards and parrots must be caged.

Each habitat is assigned a maximum capacity upon creation. This maximum number of animals may not be exceeded when populating the habitat. Attention must also be paid not to put incompatible animals into the same habitat. Zebra and gazelles can be in the same area, but neither can live with a lion. Sharks cannot be allowed near the seals, but starfish are compatible with both. Buzzards should be kept separate from parrots. Animals of the same type can always share a habitat, so there can be multiple lions in the same enclosure, multiple seals in the same aquarium, etc.

Your aim is to create and implement the required classes. This assignment is heavily focussed on design. The use of inheritance and a well chosen class hierarchy is absolutely essential! Just getting the program to pass functional tests will not give you many points!

The following steps guide you towards a clean design that significantly reduces code duplication.

 

Step 1: Download the provided code

Starter code is provided in the form of src.zip, which can be downloaded from LEARN (under Assessment → Assignment 3→ src.zip). Create a new Java project in your favourite IDE and replace the src folder with the one provided.

 

Step 2: Create the animal classes

Create a class for each animal (Lion.java, Zebra.java, etc.) inside the animals package. All of these must be related to the provided, abstract class Animal.java. As you can see from that class, every animal has a getNickname() method, which returns the name given to the animal upon creation.

For example, you could create two parrots called Polly and one called Billy (nicknames are not unique). Think about where it is best to implement this method and where the name should be stored. Now, implement the isCompatibleWith() method for each animal according to the above restrictions on sharing a habitat. The method need not cater for animals that cannot live together anyway.

 

Step 3: Create the different areas

Create: Entrance.java, PicnicArea.java, Aquarium.java, Cage.java and Enclosure.java inside the areas package. These classes must all conform to the IArea interface, but you may find it useful to create some intermediate classes in the hierarchy. For now, getAdjacentAreas() can return null.

 

Step 4: Create the zoo

Create Zoo.java in the zoo package and have it implement the provided interface IZoo. This will require adding all unimplemented methods to your code. The ones that are not needed (yet) should return null, zero or false. This is to ensure your code compiles.

 

Step 5: Add new areas to the zoo

Implement the addArea, removeArea and getArea methods in Zoo.java according to the descriptions in the IZoo interface. You will need to decide how to store and retrieve the areas that are added. Depending on your design you may (or may not) need to change other classes. You must choose some way of generating integer IDs to uniquely identify each area that is added.

How you do this is up to you. An area you have already added cannot be added again before first being removed, but you can add multiple areas of the same type by using different instances.

Finally, ensure the zoo always has exactly one entrance area with ID zero that cannot be removed. You do not need to worry about the possibility of multiple zoos being instantiated.

 

Step 6: Add animals

Now implement the addAnimal method. This method returns a byte code that indicates if the operation was successful or (if not) why it failed. Error codes are provided in Codes.java. When multiple reasons apply, the error with lowest value should be returned (as documented in Codes.java). The addAnimal method should take advantage of your other classes by delegating

 

some of the responsibility. You may find that some changes to your current design and class hierarchy are required to do so.

 

Step 7: Report on your design decisions

Explain where, how and why you made use of inheritance. This is about explaining your design, not your code! Include this in the Basic section of your report. Guideline length is 300-400 words. Note on reporting issues

Should you have difficulties completing any of the steps, you can explain your ideas in your report to get some of the credit. Please do so under separate sub-heading e.g. “Issues with step 5”. You can also report problems with partially working code, such as when it fails only for certain inputs. These sections are not required if your code is fully functional. Since the problems can vary greatly, a fixed word limit does not make sense here, but you should try to be as concise as possible.

 

Intermediate: All around the zoo

Due to an ongoing pandemic, the zoo has to adopt a one-way system for visitors moving between areas. Currently, all paths have been blocked off and it is your job to reconnect them and allow visitors to go between the different areas. The following methods need to be implemented.

 

connectAreas(int fromAreaId, int toAreaId)

After this method is called, visitors are allowed to go from the area with the fromAreaId to the area with the toAreaId. Going the other way is not possible (unless you call the method again with the arguments swapped). If fromAreaId == toAreaId, the call has no effect.

Example:

You have added one aquarium, which was given an ID of 1 and the entrance area has an ID of 0. It is not possible to go from the entrance to the aquarium until you call connectAreas(0, 1). It is not automatically possible to go from the aquarium back to the entrance, but calling connectAreas(1, 0) allows this.

 

You now also need to implement the getAdjacentAreas method of Iarea.java (the other methods in the interface will be of use). This returns all areas connected to the current area by previous calls to connectAreas. Only include areas that visitors are allowed to go to directly (in one “hop”) from the current area without breaking the rules of the one-way system.

The getAdjacentAreas method must be implemented before you proceed with any further tasks!

 

isPathAllowed(ArrayList<Integer> areaIds)

Returns true if (and only if) visitors are allowed to visit the areas in the order given by the passed in list. The path starts with the area ID at index 0 in the list. The first area in the list need not be the entrance or even reachable form the entrance, but all areas must be part of the zoo.

 

visit(ArrayList<Integer> areaIdsVisited)

A visitor passes through the rooms in the order they are listed in areaIdsVisited. They write down the names of all animals they encounter in the order they see them. Within each area, the visitor always happens to spot the animals in the order they were added to the habitat. If the same habitat is visited multiple times, they write down the names again. The list of names is returned by the method. The visitor may start taking notes from any area in the zoo (need not start at the entrance). However, if they disobey the one-way system while taking notes, the notes are confiscated and null is returned.

 

findUnreachableAreas()

This method returns the set of all IDs belonging to areas that are part of the zoo, but cannot be visited when starting from the entrance area and obeying the one-way system.

 

Report

The intermediate section of your report should cover the following:

1. Explain how you modelled the zoo’s areas and connections. (Guideline 300 words)

2. Describe an alternative (data-)representation and explain why you did not choose it. (Guideline 200 words)

 

As in the basic section, you can (optionally) report issues and ideas in the report for partial marks.

 

Advanced: Ticket machine

The zoo offers ticket machines at which visitors can pay the entrance fee in cash. The machines need to be programmed to return the correct change. Your task is to implement the payEntranceFee method of IZoo.java along with a few other (mostly trivial) methods described here:

 

setEntranceFee(int pounds, int pence)

As the name suggests, this is used to set the price of a ticket in pounds and pence. Note that you should not use floats or doubles when dealing with currency. This is due to precision issues with those types. After some numeric operations, a result that should e.g. be exactly £1 can be £0.999. Occasionally, the zoo has an open day where tickets are free (visitors still need a ticket though).

 

setCashSupply(ICashCount coins)

This method is used to stock the ticket machine with cash that it can return as change. This will require implementing the ICashCount interface, which is used to represent an amount of cash in terms of the numbers of the following notes and coins: £20, £10, £5, £2, £1, 50p, 20p and 10p. The machine does not accept smaller coins or notes larger than £20. As its name indicates, this method sets the cash supply (rather than adding to it).

 

getCashSupply()

Simply returns the ICashCount instance, which should reflect the number of notes and coins currently in the ticket machine. These counts may increase as a result of cash being inserted or decrease when change is returned.

 

payEntranceFee(ICashCount cashInserted)

The challenging part is this method, which takes as its parameter the cash that is inserted and returns an ICashCount instance representing the correct change. The contract of the method is as follows:

• If the inserted cash amounts to less than the price of a ticket (as set via setEntranceFee), the machine returns the cash that was inserted. It must return the exact same number of each note and coin (not just any equivalent amount of cash). This implies that you can (but need not) return the instance of ICashCount that was passed in.

• If too much money is inserted and the machine cannot return the exact change (due to running out of the required notes or coins), it returns the inserted cash. As above, you must return the same number of each note and coin. The inserted cash is available to the machine for making up the change.

• If the inserted cash pays for the ticket exactly, no change is given. This is indicated by returning an ICashCount instance that contains zero of each denomination. The inserted cash is added to the machine’s cash supply.

• If too much money is inserted and the machine is able to give exact change, it must do so. So as not to annoy the visitor by paying out the entire change in 10p coins, the machine will always prioritise large denominations to return the least number of notes and coins possible (given its current supply). The cash inserted by the user can be used to make up the change.

Example: A user pays for a £17.80 ticket with a £20 note. Coins adding up to £2.20 must be returned as change if at all possible. If the machine has a £2 coin and a 20 pence piece, then those must be given. If, however, the machine is out of 20p coins it returns two 10p coins instead. If it does not have those either, it returns the £20 note (no sale).

Note: In some cases it is easier to find the correct change than in others. Marks are awarded based on the types of cases your algorithm can handle. I would recommend starting with a simple approach and then improving it if you have time.

 

Testing: Adhering exactly to the specification is part of the challenge. The best way to make sure your algorithm is working is to write a few tests (the CodeGrade tests for this task are hidden).

This is optional though. There are no marks for writing tests.

Report

The advanced section of your report should cover the following:

1. Explain how you chose to represent money in your implementation of ICashCount and why.

 

(Guideline 100-150 words)

2. Explain the key ideas behind your algorithm. Give an overview of how it works, rather than explaining it line by line. (Guideline 300-500 words)

Again, you can report issues and ideas in the report for partial credit. Restrictions

The following restrictions apply to this assignment:

• Do not use any functional language constructs such as lambdas or streams.

◦ Most functional constructs are methods that take a function (or predicate) as an argument, like map, filter, reduce or removeIf.

◦ The arrow operator (→) is another indicator.

• Do not use any third party libraries.

◦ All imports starting with java.util are allowed. ◦ No other libraries allowed. Good Scholarly Practice

Please remember the good scholarly practice requirements of the University regarding work for credit. See: https://web.inf.ed.ac.uk/infweb/admin/policies/academic-misconduct

This also has links to the relevant University pages. Marking Criteria

Marks will be assigned in accordance with the University’s Common Marking Scheme (CMS). See: https://web.inf.ed.ac.uk/infweb/student-services/ito/students/common-marking-scheme

For a pass grade (up to 49%) it is sufficient to tackle the Basic section. This includes both code and report aspects, with the latter playing a significant role. Code quality is also taken into account, but to a lesser degree than in higher grade bands. The same holds true for the presentation of the report.

For a 2nd or low 1st class (up to 79%) you must first complete the the basic report and almost all basic coding features to a high standard. Only then does it make sense to address the Intermediate tasks (code and report). Quality and presentation become more important. There should be evidence of a conscious effort to produce good code and a clear, informative and structured report.

The advanced section is for those aiming at an A1 or A2 (up to 100%). At this point, all basic tasks must be well polished and almost all intermediate tasks should well solved and documented. Grades in this range require excellent code quality and a clear, well presented report that demonstrates real understanding and insight.

The report is an important part of this assignment. It can give (or lose) you a lot of marks. Even if you only have some ideas for how to approach a task, they are worth writing down.

Report

• Content

◦ Answer questions directly and to the point.

◦ Do not write down everything you know about the topic, stick to what was asked.

◦ Go beyond giving the correct answer by explaining why it is correct (shows understanding).

• Structure

◦ Break the content down into well labelled sections (see report template).

◦ If you are making an argument, ensure you organise your points into a logical sequence. ◦ Try to make the text flow by avoiding frequent or abrupt changes of topic.

• Writing style

◦ Should be clear and concise.

◦ Make the report as short as possible without sacrificing content.

◦ Avoid repetition: Make your point once and make it well, but avoid re-stating it.

 

 

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