Here are the source files:

VisibleDataStructure.java  -- the abstract class for visible data structures.

VisibleArray.java  -- the class for visible arrays.

VisibleVerticalArray.java  -- subclass of VisibleArray handling arrays that are laid out vertically.

VisibleHorizontalArray.java  -- subclass of VisibleArray handling arrays that are laid out horizontally.

SelectionSort.java  -- A class that defines an applet to demonstrate the other classes.