15-121 (Reid-Miller)

Lab 12


In this lab, you will experiment with maps and sets in Java.

EXERCISES

Download the project Lab12.zip with a class named MapSetTester with a main method. You will be using the TreeSet and HashMap classes, so open up the Java API so you can refer to the documentation for these classes as you work on these problems. (Our next lecture will cover the HashSet and HashMap classes.)

  1. In your main method, create a HashMap named networkMap that maps a TV network to the television shows from that network. That is HashMap will contain pairs where the key is a TV network name and the associated value is a TreeSet that contains television shows from that network: 

    Map<______,______> networkMap = new HashMap<______,______>();

  2. The loop reads the name of a television network and then the name of a TV show on that network from a file. Add the network and show to the hash map. That is, find the network in the hash map.

    1. If the network is not in the hash map yet, create a tree set with the name of the television show in it, and then add the key,value pair (network, set with 1 show) to the hash map.

    2. If the network is in the hash map, add the television show to the tree set for that network.

    After you update the hash map, output the contents of the hash map (i.e. System.out.println(networkMap); ). This will repeat until 10 shows have been entered.

    Sample Output (note how the networks are not necessarily in lexicographic order, but the television shows for each network are in lexicographic order... why? ): 

    TV show on FOX: The Simpsons
{FOX=[The Simpsons]}

TV show on NBC: ER
{FOX=[The Simpsons], NBC=[ER]}

TV show on ABC: 20/20
{FOX=[The Simpsons], NBC=[ER], ABC=[20/20]}

TV show on CBS: Survivor
{CBS=[Survivor], FOX=[The Simpsons], NBC=[ER], ABC=[20/20]}

TV show on ABC: Lost
{CBS=[Survivor], FOX=[The Simpsons], NBC=[ER], ABC=[20/20, Lost]}

TV show on FOX: Family Guy
{CBS=[Survivor], FOX=[Family Guy, The Simpsons], NBC=[ER], ABC=[20/20, Lost]}

TV show on CBS: CSI
{CBS=[CSI, Survivor], FOX=[Family Guy, The Simpsons], NBC=[ER], ABC=[20/20, Lost]}

TV show on FOX: American Idol
{CBS=[CSI, Survivor], FOX=[American Idol, Family Guy, The Simpsons], NBC=[ER], ABC=[20/20, Lost]}

TV show on ABC: Desperate Housewives
{CBS=[CSI, Survivor], FOX=[American Idol, Family Guy, The Simpsons], NBC=[ER], ABC=[20/20, Desperate Housewives, Lost]}

TV show on NBC: Law And Order
{CBS=[CSI, Survivor], FOX=[American Idol, Family Guy, The Simpsons], NBC=[ER, Law And Order], ABC=[20/20, Desperate Housewives, Lost]}

  3. Once you have your hash map set up, write and call a method that prints the contents of the hash map in alphabetical order by network, one network per line.

    1. Create an array list initialized with the set of keys of the hash map. (HINT: The keySet method of the HashMap class returns a set of the keys and the ArrayList has a constructor that allows you to initialize the array list using a collection (and a set is a collection)).

    2. Sort the array list. You can do this in one line.

    3. Iterate over the (sorted) array list of keys, get the corresponding value (set of TV shows) for each key from the hash map and print them out. (Note: You won't have to sort the TV shows for the network since they'll already be sorted... why?)

    Sample output: 

    ABC: [20/20, Desperate Housewives, Lost]
CBS: [CSI, Survivor]
FOX: [American Idol, Family Guy, The Simpsons]
NBC: [ER, Law And Order]

  4. Complete your tester by writing a loop that asks the user to enter a TV show and then outputs the network that maps to that TV show, if any. Otherwise report "UNKNOWN". Repeat until the user enters an empty string.

    HINT: Write a method that uses the map to lookup the network for a TV show: Iterate over each key (network) in the map, and see if its value (set of shows) contains the desired show. If so, return the network. If the TV show is not in the map return null. You don't have to worry about uppercase/lowercase, just match the TV show name exactly.

HANDIN

If you worked with another student, put both of your names in a comment at the beginning of your program. At the end of lab, create a zip file of your program and submit it to Autolab. (If you worked together, you only have to submit one program.)

FUTURE WORK: FUN STUFF FOR LATER