15-121 Homework 2: Simple Contact List - Due 9/15 at midnight
Download and unzip hw2-code.zip, which contains
slightly modified versions of the Person.java and
the Contacts.java files that we developed in class on Thursday, with
one exception. To make it more realistic (and comply with CMU's rules on
release of personal information) I have changed the nationality field to
andrewID and added some data that we talked about in class! All the code that
you write for this assignment should be added to one of these two files.
Note: You will be graded in part on your coding style. Your code
should be easy to read, well organized, and concise. You should avoid
Background: A Contact List
In this homework, you'll put the finishing touches on a primitive contacts
list, using the data in names2.txt as a database. The data in this file
consists of a person's first name, last name, andrew ID, phone number (made
up most of these) and "group". We're not quite ready to compete with
Apple, but we should be able to get some reasonable functionality even at this
stage of the course.
You will need to write the following methods in the Contacts class:
This constructor needs to be modified to work with the new data format found
Needs to be modified to correctly return a properly formatted (spaced) String
that represents the contents (used cells) of the contacts lists.
void addPerson(Person p)
Assuming there is room in the contacts list, adds Person p
after the current last element, updating numContacts appropriately.
void removePerson(String id)
Removes the entry for the person with andrew ID, id, from the contact
list, if it exists. All the entries after that person need to be moved up one
slot in the array and the number of entries in the contact list should be
decreased by one. If there is no person with the andrew ID, id, this
method should print a message to that effect.
void changeNumber(String id, int newNumber)
If a person with andrew ID, id, exists, changes the phone number that
belongs to the person with that ID to newNumber. If no such person
exists, the method should print a message to that effect.
void allInGroup(String g)
Prints all the entries in the contact list with the specified group, g.
Prints nothing if no entries match the specified group. You will need to
modify the Person class to add a method that returns a person's
group in order to do this.
void updateDatabase(String fileName)
Creates a file with name provided by fileName and writes the contents
(only the used cells) of the contact list to this file. Your file
must be written so that it can be read back in by your program.
Some of the methods you will write in the Contacts class will
require that you change/add methods in the Person class (e.g.,
removePerson will need a getID method to be added to
the Person class). Others may require a different getter or setter
(as in allInGroup).
Of course, you will also need to test your methods by calling them from main.
Submitting Your Work
When you have completed this assignment and tested your code
thoroughly, create a .zip file with your work (including both
files Person.java and Contacts.java). Name the zip file
"your-last-name".zip and email it to
Make sure to keep a copy of your work just in case something goes wrong!