Code Challenge Task #2: I don't understand exactly what is being mapped in this task.

Thanks very much!

what Grigorij Schleifer is saying is when using a Map<Key, Value> you have a key and a value because or Map is requiring a <String, Video> object we need to pass those values. vid.getTitle()// returns a String, vid// returns a Video object which we need. in the for loop we are basically saying hey videoMap put this darn title that we got from this getTitle() method into your key factory and that key is Valuable to me because it opens up my magic box Collection of Videos. weird way of putting it but it may be useful.

Hi Melissa,

You create a Map with two "parameters"

    Map<String, Video> byTitle = new TreeMap<String, Video>();
    // create am Map and declare it as TreeMap to be ordered alphabetically
    // that will give you a natural ordered collection of Titles and Videos inside the Map
    // Title as key and the Video as value

The String inside the Map is the key and it is our Title. To every key (Title) you have a corresponding value (Video) ...

or in other words:

    Map<key, value> byTitle = new TreeMap<key, value>();

or in pseudocode:

    Map<Title of the Video as key, Video itself as value> byTitle = new TreeMap<key, value>();

To your second question:

To create a Video object our Video contructor takes the title of the Video. And it is a String.

Was this helpful?

Grigorij

Hi Melissa,

sorry for the delay.

You can order Videos in a Map and "assign" to every Title (your key) the Video as the value. Your Video class constructor takes the Title "My fancy title" and creates a Video object with that title. So you are not mapping a Title to nothing. you are combining the Video with the Title during the object creation. There is no Map here ... because you haven´t created the Map yet.

Let us look at the complete videoByTitle method:

 public Map<String, Video> videosByTitle(Course course) {
        // Here you create a Map 
       // and defining the key and value
       // there is still nothing mapped to the Map
        Map<String, Video> videoMap = new HashMap<String, Video>();
        List<Video> vids = course.getVideos();
        for (Video vid : vids) {
          videoMap.put(vid.getTitle(), vid);
        // HERE you map the Title and the Video together into the Map
       // so now the title is mapped to the Video inside the Map
        }
        return videoMap;
      }

Makes sense?

Grigorij