CSC 207.02 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!
• Beware! Today is Friday the 13th (Class)
• Today is a lab day. I think it’s the right length.
• Quiz 4 returned.
  • Quizzes go to the mentor, not the recycling bin.
  • Don’t write if ((val % this.div) == 0) { return true; } else { return fal se; } 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. The following hack, which should not be necessary, seems to address the issue: add import java.lang.String; at the top of your file. Copying to another project also works in some cases.

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)
  • Put your testing code in the body of the message.

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.

Consent is essential.

Questions

I’m going to try to skip questions today so that there’s enough time for lab.

How should we partner on a GitHub repo?

Normal 207 practice vs. Normal “experienced” practice

Normal 207 practice: When I stop, push everything to the repo. When I start again, pull from the repo. Issue: If you push stuff that doesn’t work, no one has working code.

Better practice: If you’ve done work that you don’t want to push to the main branch, but don’t want to lose, you can create another branch.

You could also use forks, but that could be a bit more complicated.

Lab

The debugger is your friend! (or it can be your friend)

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

Note that you may note necessarily want to check the particular text of the exception.