coalesce work on sorting
To understand sorting, it helps to study and program a few different algorithms.
Assignments so far have asked for two implementations:
- selection sort, in hw6216
- insertion sort, in hw6916
The structure here combines this work,
in preparation for advancing it.
The structure provides an abstract class, Sorter,
that holds methods (like isSorted) needed for all
implementations of sorting.
Subclasses like InsertionSorter will implement
a particular sort algorithm.
choices in design
Sorter should not be concrete, because I know of no sensible meaning
for sort() that is independent of a sort algorithm.
The other choice, making Sorter an interface, seems unappealing because
interfaces aim to specify the behavior of a class, as Comparable does,
rather than a partial implementation of a class.
Versions of Java starting with v9 allow class and default
methods in interfaces, making this distinction less clear.
But CoBo plans to de-emphasize abstract classes and interfaces
in future years, so I should limit our use of them.
The current design is limited to String data.
That seems needlessly restrictive, since
the sorts will work equally well
on any type that can be compared to itself.
But implementing that flexibility using Java's generic classes
should remain beyond
the scope of this course, as optional extra education.