Add maps concept

[smcg468]

pull request

This issue addresses #2583

• Renamed the exercise from 'high-score' to 'arcade-high score' to avoid clashing of exercise names

• Added 'maps' to the practises and prerequisites for the 7 exercises listed in the issue

• Changed the prerequisites for the arcade-high-score concept exercise from what was on the elixir track which was

      "lists",
      "tuples",
      "anonymous-functions",
      "default-arguments"
  

to

       "numbers"
       "strings"

• Could also add an howManyPlayers task to utilise the .size() method if it would help, or maybe best to keep it consistent with the elixir track.

Let me know of any changes you'd like me to make.

Reviewer Resources:

Track Policies

[sanderploegsma]

Awesome! I'll try to review this sometime this week 👍

[sanderploegsma]

Thanks for picking this up! It already looks very good, and I left a bunch of comments mainly related to making the exercise a little bit more object-oriented, which is more in line with the Java track's policies.

Could you have a look at them and request a new review when you have addressed them?

[sanderploegsma]

Could you come up with a blurb about the exercise instead? Here's the one that the Elixir track uses:

Learn about maps by keeping track of the high scores in your local arcade hall.

[sanderploegsma]

The list of exercises is now sorted alphabetically to limit the number of merge conflicts occurring when multiple people are working on new concept exercises at the same time.

Could you move this entry to the appropriate place?

[sanderploegsma]

In my opinion this introduction into Maps should focus more on the basic operations when working with maps. Specifically, I think it should show:

• How to create a new Map instance.
• How to set values using the put method.
• How to retrieve values using the get method.

To me, the keySet and values methods are OK to mention in the about.md, but should not be introduced until a student knows how to interact with the map contents directly.

[sanderploegsma]

Personally I'd like to change this exercise to be a little bit more object-oriented. I have the following reference implementation in mind, what do you think?

class ArcadeHighScore {

    private Map<String, Integer> highScores = new HashMap<>();

    Map<String, Integer> getHighScores() {
        return highScores;
    }

    void addPlayer(String name, Integer score) {
        highScores.put(name, score);
    }

    void removePlayer(String name) {
        highScores.remove(name);
    }

    void resetScore(String name) {
        highScores.put(name, 0);
    }

    void updateScore(String name, Integer score) {
        Integer oldScore = highScores.getOrDefault(name, 0);
        highScores.put(name, oldScore + score);
    }

    Set<String> getPlayers() {
        return highScores.keySet();
    }
}

The first task would then cover defining the private highScores field and returning it in the getHighScores() method. The other tasks should speak for themselves.

[sanderploegsma]

You probably want to create a new instance for every test using @BeforeEach to make sure the SUT doesn't retain any state from a previous test, this makes the tests easier to reason about, also for students!

[sanderploegsma]

Note on these objectives: they should cover the learning objectives from the exercise, not the concept. I believe this exercise doesn't cover the different implementations of the Map interface, nor how to retrieve all items in a map.

[sanderploegsma]

We can probably cover all future additions of Map implementations in Java by summarizing this as "Other implementations of the Map interface"

[sanderploegsma]

Technically I don't think string formatting is used in this exercise, so maybe strings doesn't have to be a prerequisite.

[sanderploegsma]

We should probably (also) check that it's empty.

[sanderploegsma]

I think we need to add a second test for this task that verifies the requirement when updateScore is called with a player that doesn't exist in the map yet.

[sanderploegsma]

@smcg468 Are you still working on this? Leave a comment if you are, otherwise I'm going to close this due to inactivity.

[smcg468]

@smcg468 Are you still working on this? Leave a comment if you are, otherwise I'm going to close this due to inactivity.

Yes still working on this, been quite busy over Christmas but should get back to it soon

[sanderploegsma]

@smcg468 Are you still working on this? Leave a comment if you are, otherwise I'm going to close this due to inactivity.

[smcg468]

@sanderploegsma Sorry yes will get back to it this weekend

[sanderploegsma]

Take your time! I didn't mean to rush you, but I figured you may have lost track of this PR 😉

[manumafe98]

Hey @smcg468! we will like to know if you need help finishing this PR! it's an interesting concept to be added to the java track, so if you are busy with work we can give you a hand with it! Thanks for your time 😃

[sanderploegsma]

@smcg468 I see you've been busy, nice!

Since some of the CI jobs are still failing I'm going to assume that you're still working on addressing the feedback. Just make sure to hit the 're-request review' button on this PR once you're done, so I know it's ready for another look. 😉

[manumafe98]

hey @smcg468 do you need some help with this pr?