Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

top(k):
Return an iterable collection of the k most accessed elements.
6.5.1 Using a Sorted List and a Nested Class
The first implementation of a favorite list that we consider (in Code Fragments
6.19–6.20) is to build a class, FavoriteList, storing references to accessed
objects in a linked list ordered by nonincreasing access counts. This class also uses
a feature of Java that allows us to define a related class nested inside an enclosing
class definition. Such a nested class must be declared static, to indicate that this
definition is related to the enclosing class, not any specific instance of that class.
Using nested classes allows us to define "helper" or "support" classes that can be
protected from outside use.
In this case, the nested class, Entry, stores, for each element e in our list, a pair
(c,v), where c is the access count for e and v is a value reference to the element e
itself. Each time an element is accessed, we find it in the linked list (adding it if it is
not already there) and increment its access count. Removing an element amounts to
finding it and taking it out of our linked list. Returning the k most accessed
elements simply involves our copying the entry values into an output list according
to their order in the internal linked list.
Code Fragment 6.19: Class FavoritesList.
(Continues in Code Fragment 6.20.)
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