Homework 1: Contact List

Due Monday, 4-Sep @ 8:00pm on Gradescope

This assignment will help you refresh your programming abilities and get you a basic introduction to Java. You should start early so that you can attend office hours when problems come up.

For this assignment you have 7 submissions. You should write your own testcases while you work so that you don’t waste submissions. There are some example testcases provided that you can use to get started.

After you have used your submissions, you may continue to submit, but your submission will be penalized 4 points for every extra submission. (So, your 8th submission receives a -4, your 9th submission a -8, etc.)

1. Introduction

In this assignment, you’ll build a simple contact list that uses an array-based data structure to grow larger as needed. We’re not writing the next Microsoft Outlook here, but we’ll get a basic contact list up and running.

Download the pre-prepared Eclipse Project hw1.zip and import it into Eclipse using these instructions. You will make all of your changes inside of Contact.java, ContactList.java, and ContactListTester.java.

2. Contact Class

The Contact class should represent a single contact. You need to fill in the Contact class with everything required to store and manage a single contact. You will need relevant instance variables, at least one constructor, and methods (including a toString).

There are comments inside of Contact.java to give you some hints.

3. ContactList Class

You will be implementing a simple contact list that grows dynamically to hold more contacts as needed. It also has some methods to manipulate or rearrange those contacts.

You will store the contacts in an array, but arrays in Java have a fixed size defined when they are created. That means that if your array is full and you still need to add another contact to it, you will need to create a new, larger array, copy all of the old contacts to it, and then add your new contact. As a consequence of this, your array may have more “space” available than there are values currently stored. To keep track of which spaces in your array have valid integers and which don’t, you will also be tracking how many contacts are actually stored in the array.

Inside the file ContactList.java you will find method declarations with empty bodies. You need to implement each incomplete method and write code to test them inside of ContactListTester.java.

You are free to add new methods to either file (such as helper methods) but do not change the names of any of the provided methods. If you do, you will automatically fail the autograder.

The methods you are writing are as follows:

public boolean isEmpty()

Determines if the ContactList object is empty or not

  • Returns: true if there are no contacts in the array, and false otherwise


public boolean isFull()

Determines if the ContactList object is full or not

  • Returns: true if array is full and false otherwise


private void enlarge()

Optional: A helper function you should consider writing. If the ContactList is currently full, then resize it to be double its current size. To do this, you’ll need to create a new, larger array, and copy the existing items into it.


private int findContact(String id)

Optional: A helper function you should consider writing. Having it might help you with some of the below methods. You can probably figure out what it should do…


public boolean addContact(String andrewId, String firstName, String lastName, String phone)

Add a contact to the contact list. Verify that the new Contact has a unique andrew ID and, if so, add the contact after the current last element, updating numContacts appropriately.

  • Parameters:
    • andrewId — The andrewId of the contact
    • firstName — The firstname of the contact
    • lastName — The lastname of the contact
    • phone — The phone number of the contact
  • Returns: True if the contact was successfully added and false otherwise


public boolean insertContactAtLocation(int loc, String andrewId, String firstName, String lastName, String phone)

Adds a new contact to the contact list, making sure it is at location loc of the array. This does not replace an entry in the contact list, instead, it inserts the new contact into that location, shifting other contacts as needed.

Only insert the new contact if there are no existing contacts with the same andrew ID already in the contact list and the loc argument is reasonable. (You can’t, for example, insert at a negative index or insert at an index that would leave gaps in the array.)

e.g., If the array contained [nkuwari, awaatif, jpritch] and this method was called to insert kfrank, then the array would contain [kfrank, nkuwari, awaatif, jpritch].

If the array is full before inserting, you should resize it first to be double its current size.

Don’t forget to update the instance variable that tracks how many items are stored in the array.

  • Parameters:
    • loc — The index where the new contact should be in the array
    • andrewId — The andrewId of the contact
    • firstName — The firstname of the contact
    • lastName — The lastname of the contact
    • phone — The phone number of the contact
  • Returns: True if the contact was successfully added and false otherwise


public void removeContact(String id)

Remove a contact from the contact list. If there is no contact with the requested andrewId then this method should do nothing. When removing the contact, other contacts in the array will need to be shifted to ensure there are no “gaps” in the array.

  • Parameters: id — The andrewId of the contact to remove


public boolean changePhone(String id, String newNumber)

Change the phone number of a contact.

  • Parameters:

    • id — The andrewId of the contact whose phone number should be

      changed

    • newNumber — The new phone number

  • Returns: True if the number was successfully changed and false otherwise


public void rotateLeft()

Rotates all the elements in the contact list one position to the left, placing the first element into the last position.

For example: if the contact list before the call to rotateLeft is [kfrank, nkuwari, awaatif, jpritch] it is [nkuwari, awaatif, jpritch, kfrank] after the call


public void reverse()

Reverses the elements stored in the array

For example: if the array before the call to reverse is [nkuwari, awaatif, jpritch, kfrank] it is [kfrank, jpritch, awaatif, nkuwari] after the call


4. Grading and Submission

Your submission will be graded as follows:

  1. For the first 90 points, your submission will be auto-graded on Gradescope.

  2. For the next 5 points, your submission will be manually graded to check for good implementation methodologies. (Did you use a good approach to solving the problems?)

  3. For the next 5 points, your submission will be manually graded to check for good testcases that you include in ContactListTester.java. (Do you have 2-3 of your own testcases for each method, and do they all execute automatically?) There are two testcases already included to serve as examples.

  4. Your code will also be checked for style. The parts of style that can be checked automatically (things like spacing, indentation, the use of CamelCase, etc.) are automatically checked by the autograder. Other parts of style, such as choosing good variable names, will be checked manually. Autograded style guide violations can result in, at most, -10 points. Manually checked style guide violations can result in, at most, -5 points.

You will submit your program to Gradescope. Log in to the system and you will see the homework. Once there, you need to submit a zip file containing your code. Lucky for you, however, Eclipse can create this zip file for you. Look at these instructions for exporting. On Gradescope, you’ll submit that exported zip file. On the page that follows your submission, you will see your live score (out of 90). It may take up to a few minutes for your score to appear. If you receive a lower score than you expect, you can click on the individual testcases to see the feedback from the autograder.

You must follow the model of our testcases from previous assignments (meaning you print when you start, print the results (pass/fail) when you finish, etc.) Additionally, you must comment each testcase with a note describing what it tests.

5. Restrictions

You may only use the following Java libraries in this assignment:

java.util.Random
java.util.Scanner
java.io.FileReader

6. Important Notes