Grouping objects - Objects First with Java: A Practical Introduction Using BlueJ - page 99

Figure 4.1
A MusicOrganizer
containing two file
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Figure 4.2
A MusicOrganizer
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We notice that the MusicOrganizer object looks quite simple—it has only a single field that
stores an object of type ArrayList<String> . All the difficult work is done in the ArrayList
object. This is one of the great advantages of using library classes: someone has invested time
and effort to implement something useful, and we are getting access to this functionality almost
for free by using this class.

At this stage, we do not need to worry about how an ArrayList is able to support these fea-
tures. It is sufficient to appreciate just how useful this ability is. Remember: This suppression of