CSC 207.01 2019S, Class 13: Array-based linear structures

Overview

• Preliminaries
  • Notes and news
  • Upcoming work
  • Extra credit
  • Friday PSA
  • Questions
• Lab

Preliminaries

News / Etc.

• Continue partners from Wednesday!
• Mentor Session Sunday at 8 p.m.
• Beware! Today is Friday the 13th (Class)
• Today is a lab day. I think it’s the right length.
• Quiz 4 returned.
  • Don’t write if ((val % this.div) == 0) { return true; } else { return false; } Write return (val % this.div) == 0;
  • Subtype polymorphism and parameteric polymorphism don’t always mix well. If C implements I, you cannot assign a value of type Box<C> to a variable of type Box<I>.
• Recommended approach to starting homework (after reading)
  • Create a project in Eclipse, choosing an appropriate place for the directory.
  • Add your primary package (if there is one).
  • Create a repo on GitHub (no README)
  • cd to that directory
  • Follow the GitHub instructions for linking the directory to the repo.
  • Add all the files Eclipse generates.
  • Push.
  • Share the repository with your partner and me.
• Some of you are getting messages like Integer type is not visible and String type is not visible in Eclipse. I have no idea why and can’t usually reproduce the issue. I’ve found that creating a new repo and copying files into that often fixes it. Once again, I’m not sure why.
  • My suspicion: Some of the code came from copying-and-pasting from Office365, and that sometimes inserts hidden characters.

Upcoming work

• Assignment 5 due Thursday night.
• Readings for Monday
  • Iterators (Not available until tomorrow night.)
  • Anonymous inner classes (Not available until tomorrow night.)
• Lab writeup: Exercise 6
  • To csc207-01-grader@grinnell.edu
  • Subject: CSC 207.01 Writeup for Class 13 (Your names)

Extra credit

Extra credit (Academic/Artistic)

• Iowa Flautists in Concert. Saturday, 23 February 2019. 3:45 p.m. Sebring-Lewis Hall.

Extra credit (Peer)

Extra credit (Wellness, Regular)

• 30 Minutes of Mindfulness at SHACS every Monday 4:15-4:45
• Any organized exercise. (See previous eboards for a list.)
• 60 minutes of some solitary self-care activities that are unrelated to academics or work. Your email reflection must explain how the activity contributed to your wellness.
• 60 minutes of some shared self-care activity with friends. Your email reflection must explain how the activity contributed to your wellness.

Extra credit (Misc)

Other good things

Friday PSA

Be good. Be well. Be true to yourself.

Get consent.

Questions

Lab

Remember that the debugger is your friend!

Things you will likely want to fix/update, particularly as you implement wrap-around.

• The calculation of this.back(). See below for a thought question.
• How to keep this.front in the range 0..this.values.length-1. See below for some notes.
• The isFull() method.

if (this.front is 5) and
   (this.size is 6) and
   (this.values.length is 8)
what should this.back() return?

Ways to handle wrap-around with this.front

• Strategy one: Always use this.front % this.values.length
• Strategy two: When you increment this.front, mod by this.values.length.

Sam thinks strategy two is much better.

Checking for exceptions

Here’s an example about testing for exceptions from the JUnit 5 User Guide. It uses a feature that you don’t quite know yet (the () ->), but just assume it’s necessary syntax and we’ll go from there.

    @Test
    void exceptionTesting() {
        Exception exception = assertThrows(ArithmeticException.class, () ->
            calculator.divide(1, 0));
        assertEquals("/ by zero", exception.getMessage());
    }

Here’s how Sam traditionally tests for exceptions.

    @Test
    void testException() {
      try {
        calculator.divide(1,0);
        fail("Division did not throw an exception");
      } catch (ArithmeticException ae) {
        assertEquals("/ by zero", ae.getMessage());
      } // try/catch
    } // testException