Assignment 1 Solution

Motivation



In CS 445, we often discuss the importance of data structure design and implementation to the wide variety of computing applications. Despite decades of study and development of common libraries, organizations must still regularly develop custom data structures to ful ll their applications’ speci c needs, and as such the eld remains hugely relevant to both computer scientists and software engineers.




In this assignment, you will implement two data structures to satisfy their speci cations, which are provided in the form of interfaces.










Note: Your goal in this assignment is to write classes that faithfully implement the ADTs described in the interfaces. Sample client code is provided as one example of how the classes may be used. However, this sample code does not test all of the capabilities you are asked to implement, and thus your goal is not simply to make this sample code work. You are strongly encouraged to write your own test client as well, to further test that all operations of your classes work in all the corner cases described in the interfaces.










Provided code



First, look over the provided code. You can nd this code on Pitt Box in a folder named cs445-a1-abc123, where abc123 is your Pitt username.




The SetInterface<E interface describes a set, a data structure similar in concept to a bag except that it does not allow duplicates. It is a generic interface that declares abstract methods for adding an item, removing an item (speci ed or unspeci ed), checking if the set is empty, determining the number of items in the set, and fetching the items from the set into an array. You should not modify this interface.




The SetFullException class is included to allow potential implementations of SetInterface that have a xed capacity. Your implementation should not be xed capacity, and thus should not throw this exception.

The GroceryItem class is a simple way of representing a grocery item and its quantity. This class contains two constructors, a getter and setter for the quantity, a getter for the







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description, and some utility methods (for checking equality and converting to string for printing). Note that two GroceryItem objects are considered \equal" if they have the same description, even if their quantity is di erent! You should not modify this class.




The GroceriesInterface interface describes a collection of GroceryItem objects. Its intention is to be used similarly to a shopping list, although it is not a truly a list ; it is to be backed by the Set class, so it is unordered and does not permit duplicates. It declares abstract methods for adding and removing (i.e., increasing or decreasing quantity for) GroceryItem objects in the collection. It also has a method for overwriting the quantity on a GroceryItem, as opposed to strictly increasing or decreasing it. Finally, it has a method to print all items in the collection.




The GroceriesExample class (not in the cs445.a1 package) shows one example usage of the Groceries data structure. It demonstrates a few features, but is not a thorough test.




Tasks



3.1 Implement Set, 65 points




Develop the generic class, Set<E, a dynamic-capacity array-based implementation of the Set ADT described in SetInterface<E. Include this class in package cs445.a1. Read the comments in the interface (and this document!) carefully to ensure you implement it properly; it will be graded using a client that assumes all of the functionality described in the SetInterface, not just the behavior you need to implement GroceriesInterface!




You must include a constructor public Set(int capacity) that initializes the array to the speci ed initial capacity, and a constructor public Set() that uses a reasonable default initial capacity. Finally, you should provide a constructor public Set(E[] entries) that initializes the set to include each of the provided entries. Note that this constructor must still create its own backing array, and not adopt the argument as a data member; it must also skip all duplicates and null values in the provided array, to satisfy the data structure’s usual assumptions. Whenever the capacity is reached, the array must resize, using the techniques discussed in lecture (i.e., you should never throw SetFullException).




Method
Points


Set()


4


Set(int)
4


Set(E[])
9
int getSize()
4
boolean isEmpty()
4
boolean add(E)
7
E remove(E)
7
E remove()
6
void clear()
5
boolean contains(E)
6
Object[] toArray()
9
























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3.2 Implement Groceries, 35 points




Develop the Groceries class, an implementation of the ADT described in GroceriesInterface. Include this class in package cs445.a1. Read the interface carefully (including comments) to ensure you implement it properly. As with Set, it will be graded using a client that expects the full functionality described in its interface. The Groceries class can be seen as a client of the Set data structure. Use composition with your Set<E class to store the items as a data member of type Set<GroceryItem. Include a constructor public Groceries() that initializes the set.






Method


Points
Groceries()
3
void addItem(GroceryItem)
7
void removeItem(GroceryItem)
7
int modifyQuantity(GroceryItem)
9
void printAll()
9






3.3 Testing




GroceriesExample is provided as an example client of the Groceries class. It does not exhaustively test the functionality of both classes you must write. You are responsible for ensuring your implementations work properly in all cases, even those not tested by GroceriesExample, and follow the ADTs described in the provided interfaces. Thus, it is highly recommended that you write additional test client code to test all of the corner cases described in the interfaces. For help getting started, re-read the section of the textbook starting at Chapter 2.16.







Note: For functionality that cannot be tested (e.g., methods that crash, cannot be compiled), up to 1/2 points will be awarded by inspection. At this level, turning in code that crashes or does not compile is not acceptable and will not yield success.










Submission



Upload your java les in the provided Box directory. If you accidentally overwrite the provided interfaces or GroceryItem class, remember to restore them to their original versions. You may not make changes to the functionality in these les.




All programs will be tested on the command line, so if you use an IDE to develop your program, you must export the java les from the IDE and ensure that they compile and run on the command line. Do not submit the IDE’s project les. Your TA should be able to download your cs445-a1-abc123 directory from Box, and compile and run your code as discussed in Lab 1. For instance, javac cs445/a1/Groceries.java should compile your Groceries class. In addition, javac GroceriesExample.java and java GroceriesExample must compile and run GroceriesExample.




In addition to your code, you may wish to include a README.txt le that describes features of your program that are not working as expected, to assist the TA in grading the portions that do work as expected.













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Your project is due at 11:59 PM on Thursday, September 27. You should upload your progress frequently, even far in advance of this deadline: No late submissions will be accepted.


















































































































































































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