For students who are using Visual J++:

   This compiler does not support the Comparable interface.  What you may
do to get around this problem (aside from moving to another compiler) is
this --

   Define your own Comparable interface, as suggested by Section B.2.3 of
the text.  Define ClassCastException to extend RuntimeException.  Do throw
this exception when appropriate, but don't worry about catching it.

   Define your own wrapper classes MyInteger and MyString that implement
this interface.  In addition to the compareTo method, they will need
constructors (taking an int and a String respectively), and toString
methods.

   In the test file A2.java, replace the calls to new Integer by calls to
new MyInteger.  Wrap all of the String arguments to insert in calls to new
MyString, e.g.       
               b.insert(new MyString("8"));
These are permissible modifications of the test file.