This tutorial consists of exercises on the visitor pattern discussed in class. It also helps you prepare for the second homework.
Once again, we will be writing code for lists.
First, copy all the Java source code from the directory
~comp212/public_html/01-spring/labs/03/.
Do not copy the code in the visitor
subdirectory.
We will use this as the starting point.
Note that all the code is in the packages list and
list.visitor.
For this latter class, this means that there is a visitor
package within the list package. Corresponding
to that, there is a visitor directory within the
list directory.
Browse the code to get familiar with it, before modifying it in the following exercises.
Write a visitor called Length to compute the length
of a list using direct recursion and without using
helpers. This visitor corresponds to the
method length() of the original version of lists.
Write a visitor called GetMin to find the minimum
element of a list, assuming it contains only
Integer objects. GetMin
should use a helper visitor called HelpGetMin
to compute the minimum. This
corresponds to the getMin() method shown in class.
Write a visitor called Sum to compute the sum of the
elements of a list,
assuming AList contains only Integer
objects. Write one version using direct recursion, and one
version, called GetSum, using a helper visitor
called HelpGetSum.
Compare your resulting code with that in the provided visitor
subdirectory.