Labs

In these labs we will use Maps to store and then retrieve data.

  1. The program com.example.mapinterface.labs.AreaCodeLister reads in abbreviations.txt and areacodes.txt. Modify that program so that it loads the data from these files into two HashMaps. Then, print out each area code followed by the full name of the state or province associated with it.

Hints: * Use String.split() to parse the key-value pairs separated by tab, '\t', characters. * Look at the data. What values are unique, so they could be used as keys? What values are in both files?

(Solution: AreaCodeLister.java)

  1. Change your solution to the previous lab so that your output is sorted by area code.

(Solution: AreaCodeListerSorted.java)

  1. (Optional) The file names.txt at the root of the MapInterface project contains many names, but there are duplicates. We want to create a Map of unique names, grouped by first letter.

List of Map

Note that the names are not sorted in each row.

When you have removed duplicates and separated the names, print the list of names to the screen so that each group is on a single line.

Hints: * This Map will map String or Character keys to List<String> or Set<String> collections, depending on your implementation. * Maps of Collections use a common pattern. * When your application sees a letter that starts with B, for example, it has to check if there is a Collection for key B. If not, it creates the Collection and puts it in the Map for key B. * Then it can add the name to that Collection. * The next time it sees a B name, it checks for a Collection for key B, finds one, and adds the name to it.

(Solution: NameSeparatorMapApp.java)

  1. (Optional) Can you sort each row of names alphabetically?

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