CSSE 220 – Object-Oriented Software Development

Homework 21

Objectives

Practice object-oriented design.

Tasks

1. If you haven't already done so, do the quite brief Cycle 0 Evaluation of Team Performance survey on Angel, under Lessons → Assignments (at the top of the list).
   • Please complete this item ASAP; don't wait until this homework is due.
2. Complete the assigned reading for the next session: Big Java §13.4–13.5 and §14.1–14.3.
   • As you read, see if you can answer the self-check questions.
   • Bring your questions to class!
3. Complete the assessment exercises over this reading on ANGEL (under Lessons → Assignments).
4. Team Assignment: Working with your team, complete the assigned milestone of the Vector Graphics:
   • Per the milestones chart in Vector Graphics, this means:
     • Complete all Cycle 1 code deliverables — the code and status report (and at the end of Cycle 1, do the Cycle 1 Evaluation of Team Performance survey on Angel).
5. Solo programming: Make a “good faith effort” on the following exercises from the Recursion project that you checked out in class. Your solutions to all the following must be recursive.
   • This exercise is not due until Session 23 (Tuesday).
   • However, you are expected to attempt the exercises, so that you can bring your questions to class.
   • Don't get stuck on these exercises! Give them a try, and then bring questions to class!
   • Recursion is very easy once you have the hang of it, but very hard until that point. Take advantage of the extra time on these exercises by attempting them before Monday, bringing your questions to class.

   1. Complete the isPalindrome() and isPalindrome(int first, int last) methods in the Sentence class of the examples package, if you have not already done so.
   2. Implement, including JUnit tests, the reverse() method in the Sentence class.
   3. Complete the recursive drawSierpinski() method in the SierpinskiRenderer class in the sierpinski package. This method should render the Sierpiński Triangle as shown in the figure below. The triangle is rendered by following these steps:
      1. Draw a solid equilateral triangle.
      2. In a contrasting color, draw another solid equilateral triangle whose corner points are the midpoints of the original’s sides.
      3. Repeat this process recursively for each of the three corner triangles. That is, you will need three recursive calls in your method.
      4. Technically speaking, this process is repeated an infinite number of times to create the true Sierpiński triangle, but we don’t have that much time. So, stop your recursion when the length of a side of the triangle becomes shorter than some fixed constant, say 5.
      

   Turn-in Instructions

   Turn in your programming work by committing it to your SVN repository.