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

A Class for High Scores
Suppose we have some high scores that we want to store in an array named
entries. The number of scores we want to store could be 10, 20, or 50, so let us
use a symbolic name, maxEntries, which represents the number of scores we
want to store. We must set this variable to a specific value, of course, but by using
this variable throughout our code, we can make it easy to change its value later if
we need to. We can then define the array, entries, to be an array of length
maxEntries. Initially, this array stores only nullentries, but as users play
our video game, we will fill in the entries array with entries, but as users play
our video game, we will fill in the entries array with references to new
GameEntry objects. So we will eventually have to define methods for updating
the GameEntry references in the entries array.
The way we keep the entries array organized is simple—we store our set of
GameEntry objects ordered by their integer score values, highest to lowest. If
the number of GameEntry objects is less than maxEntries, then we let the
end of the entries array store null references. This approach prevents having
any empty cells, or "holes," in the continuous series of cells of array entries
that store the game entries from index 0 onward. We illustrate an instance of the
data structure in Figure 3.1 and we give Java code for such a data structure in
Code Fragment 3.2. In an exercise (C-3.1), we explore how game entry addition
might be simplified for the case when we don't need to preserve relative orders.
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