Why is getWords return type changed to List from Arrays

List is an interface. It can hold a reference to different types of List implementations.

The Arrays Class provides methods for manipulating arrays. The asList() method returns a fixed-size list backed by the specified array. (Changes to the returned list "write through" to the array.)

The ArrayList class is a resizable-array implementation of the List interface.

Therefore, these are not the same types of List objects.

I think Dennis used Arrays.asList() in his video example to get a fixed-length list that could be referenced as a List type. A developer using his class really should not be able to add words to a list from a getter method. Of course, a developer should not be able to set words either, but a list from Arrays.asList() allows that. Furthermore, encapsulation violations are easily committed by having public methods that just return array references. This is because the array is now accessible even after the method call where it should be out of scope. It is especially true when the array is a private member variable of the class. It is better to place the words into a new ArrayList and return it. This prevents encapsulation violation and provides uniformity.

Arrays.asList() returns a list that is not uniform with the other methods even though it is being held in a List interface as a reference. A List interface type can hold a reference to the fixed size list that Arrays.asList() returns. It is not completely uniform though because the other methods returned are ArrayLists. One can return an actual arrayList type though:

public List<String> getWords() {
    String[] words = mDescription.toLowerCase().split(“[^\\w#@‘]+”);
    ArrayList<String> wordList = new ArrayList<String>(Arrays.asList(words));
    return wordList;
}

This would be more uniform with the other methods because they would all now have the same functionality.

I hope this helps.

Regards,

Chris