Java Data Structures - Using a map to store contact methods challenge

This is a three part challenge.

Link to challenge:

http://teamtreehouse.com/library/java-data-structures/efficiency/using-a-map-to-store-contact-methods#

It starts out with:

Challenge Task 1 of 3

In the next couple of steps, let's fix up this work in progress Contact model. This is going to be used in a Web application where the user can add different ways to contact a person.

In this first step, modify the addContactMethod method to store the information in the mContactMethods Map.

The code you are given is for starters is:

  public void addContactMethod(String method, String value) {
    // TODO: Add to the contact method map
  }

So naturally if you are told to 'Add' you use add:

  public void addContactMethod(String method, String value) {
    // TODO: Add to the contact method map
    mContactMethods.add(method, value);
  }

Wrong!

So you go looking at the video and the code in the zip downloads for the course.

Here's why you won't find the answer in either place.

Both the SongBook.java code in the video and the SongBook.java code in the zip download use Array lists (not HashMaps).

Totally bogus!

By the way - hashmaps are not some great new invention by the guys/gals at TeamTreehouse.

Way back in the early versions of Windows (before the Registry), there were something called ".ini files" (where "ini" was short for initialization I guess).

They used not only keys and values but had 'sections' as well.

I imagine using hashmaps/hashtables was around even before then even though Wikipedia doesn't give much history on them:

http://en.wikipedia.org/wiki/Hash_table

It does say:

In computing, a hash table (hash map) is a data structure used to implement an associative array, a structure that can map keys to values.

Yes, you can use the term "associative arrays" to confound and impress your non-programmer friends.

.

Thus hashmaps are pretty common knowledge in the programming world and I can go 'aroamin' on the internet to try and find some info on the Java implementation of the use of hashmaps.

Specifically I ended up relying on StackOverFlow to supply the information missing from the course content,

as per usual, the alternate source for code documentation whenever

there is a "disconnect" between what is presented in the Treehouse course videos

and what the particular challenge question is asking about.

.

Here's the StackOverFlow thread I (eventually) found:

http://stackoverflow.com/questions/11048783/java-hashmap-key-value-storage-and-retrieval

Notice the 'hm.put' statements for entering keys/values into the hashmap.

So replace '.add' with '.put' in the above code snippet and you should be good to go

(but of course you had to go outside TeamTreehouse to find that out)

Does the "bogus-ness" (bogosity?) end there?

Of course not..here's part 2 of the challenge:

Challenge Task 2 of 3

In this task, let's fix the getAvailableContactMethods method. We want to return a set of the currently defined contact methods.

HINT: How about a set of the keys from mContactMethods?

I know what you are thinking:

They actually gave us a HINT, so this one should be a slam-dunk, right?

Wrong!

Of course you immediately try:

  public Set<String> getAvailableContactMethods() {
    // FIXME: This should return the current contact method names.
    Set names = mContactMethods();
    return names;
  }

Such code tries to follow the FIXME instruction to the letter

(even throwing in a 'set' like the HINT mentioned).

Of course you get a "Bummer!" message

How foolish of you to believe that a HINT would actually give you all the information you need!

So where do we go to get the missing piece of code information?

You guessed it - StackOverFlow:

http://stackoverflow.com/questions/8909810/how-to-print-all-key-and-values-from-hashmap-in-android

See the line of code that says:

Set keys = map.keySet();  

There's your real hint '.keySet()' is the missing piece of info you need to figure out what code the challenge wants:

  public Set<String> getAvailableContactMethods() {
    // FIXME: This should return the current contact method names.
    Set keys = mContactMethods.keySet();
    return keys;
  }

Note: I ended up using 'keys' (in the code snippet above) for the variable instead of 'names' just because :

1.) It seemed better suited to using hashmap's terminology

2.) The HINT (although not quite "hint-ful" enough) did actually mention 'keys'

Yes, (disclaimer for those code purists out there) it could have been done in one line instead of two.

Onward...

Challenge Task 3 of 3

For this task, let's fix the getContactInfo method.

That seems like a short and easy thing to fix...let's look at what they are giving us for starter code:

  public String getContactInfo(String methodName) {
    // FIXME: return the value for the passed in *methodName*
    return null;
  }

So reading the comment, the answer is clearly:

  public String getContactInfo(String methodName) {
    // FIXME: return the value for the passed in *methodName*
    return methodName;
  }

Having been "twice bitten" you are naturally a little "gun shy"

(even if it seems totally obvious).

With great trepidation (and a little hesitation) you press the "Check Work" button

Bummer!

AAAArrrrrggghh!

Even though you know its useless you re-watch the video and look at the code in the project's zip download one more time.

Inside SongBook.java you do find something that looks promising in these lines:

    Map<String, List<Song>> byArtist = new HashMap<>();
    for (Song song : mSongs) {
      List<Song> artistSongs = byArtist.get(song.getArtist());

Hmmm..there's actually something that uses '.get' in connection with a new HashMap.

Could this be real?

Are you actually "getting" a break (bad pun intended)

Quick check on StackOverFlow to confirm:

http://stackoverflow.com/questions/1789679/get-string-value-from-hashmap-depending-on-key-name

Yes!

'mContactMethods', because it uses a HashMap, has a built-in 'mContactMethods.get()' method that you probably can pass in the 'methodName' parameter.

So this challenge forced me to research how to work with HashMaps in Java even though it was never actually fully explored in the Java Data Structures course.

Hope reading through all this helps someone understand a little more what the challenge is looking for..

All of which leaves me thinking...maybe, instead of spending all that time producing videos they should just say:

Here's your course topics --now go explore the whole internet, and when you are ready to take the challenges come back and will have some doozies for you to puzzle out.

Then all the points can be assigned to just solving the challenge puzzles instead of endless hours watching confusing videos that don't explain things fully.

Yow!

Reading that over I sound really whine-y and cynical.

Must be tired --time for bed.

Good night all.

ZZZZZZZZZZZZzzzzzzzzzzzzzzzzzz