CS 10: Winter 2016

Short Assignment 9
Due: Monday, February 8

Assignment

This assignment will give you practice with sets and maps. The program StatesAndCities.java is the skeleton of a program that allows you to add (state, city) pairs to a database of such pairs. They are stored in a Map keyed on state names. The corresponding value is a Set of city names that are within the state. I have replaced method bodies by the comment:

// *** Your Code Here ***.

Your job is to complete the method bodies to make this program work correctly.

Helpful notes

HashMap is a class in java.util that implements the Map interface. Thus, to create an empty map where each key is a string (for the state name) and each value is a set of strings (for the names of cities in the state), you write:
HashSet is a class in java.util that implements the Set interface.
If x is your map (that maps a state to a set of cities), returns the set of keys in x. You can obtain an iterator on this set (using the iterator() method of Set), and then use the iterator's hasNext() and next() methods to obtain each key (i.e., each state) in the map x.
You can consult the online Oracle's documentation to see all the methods supported by the Map and Set interfaces.

Sample run

A sample run of the finished program is:

Command (q, a, i, P, ?): a Enter state: NH Enter city in the state: Concord Command (q, a, i, P, ?): a Enter state: NH Enter city in the state: Hanover Command (q, a, i, P, ?): a Enter state: MA Enter city in the state: Concord Command (q, a, i, P, ?): a Enter state: MA Enter city in the state: Boston Command (q, a, i, P, ?): a Enter state: VT Enter city in the state: Burlington Command (q, a, i, P, ?): i Enter state: NH Enter city that might be in the state: Concord Concord is in NH Command (q, a, i, P, ?): i Enter state: VT Enter city that might be in the state: Concord Concord is not listed as being in VT Command (q, a, i, P, ?): P MA: Boston Concord NH: Concord Hanover VT: Burlington Command (q, a, i, P, ?): q Bye

Extra Credit

There are many types of elections. In class we looked at instant runoff voting, but there are also regular voting (only first vote on ballot counts; winner is the candidate with the most votes) and approval voting (all candidates on the ballot get a vote; winner is the candidate with the most votes). Modify InstantRunoffOO.java, Ballot.java, Election.java, and VoteTally.java to handle these types of elections as well. After a set of ballots has been read report the winner under each of the three systems.

Canvas submission