Overview

• Prelim
  • Admin.
  • About HW 3
  • About HW 2
• ADT Design
• Arrays

Admin

• A final reminder to register for the 2nd-year retreat. It looks like a good opportunity to do lots of things - talk more about group work, learn from alums, think about choosing a major, etc.
  • Email [greggjol] to get the links
• It sounds like there was some demand that I focus on the syntax and semantics of imperative Java, so I've rearranged the syllabus (including today) to go over it.
  • Rearranging stuff put me even further behind! Readings may not be ready in time, and class sessions will probably focus on lecture + discussion + recitation.
  • And my class outlines may not be as deep as they usually are.
• Reminder: Mentor session Wednesday night at 8pm
• Readings for Wednesday (expect them later today):
  • Strings in Java
  • Numbers in Java
• Homework 3 is ready!
• EC opportunities:
  • Humanities Center Speaker Sarah Hendron, Wednesday, 7:30 p.m., JRC101 Waking the Machines: Art, Design, and Adaptive Technology
  • Learning from Alumni 2:15-4:05 Thursday: Ian Lunderskov '08
  • Tentative Thursday Extra: Matt Atherton '95
  • CS Table, Friday: Trusting Trust.
  • More?

About HW 3

See the homework. Lots of chances for extra credit.

About HW 2

• Many 4-5 hours
• Lots of problems with Eclipse and Git(Hub)
  • Pull requests are a pain
    • So add an administrator (easier for you than for me)
  • Pulling changes was hard
  • Debugger is hard
    • Write experiments, rather than unit tests, when you want to debug
  • What's the workspace?
    • A default place to store stuff, including config (I believe)
    • I'd recommend ~/workspace
    • But your projects generally won't go in the workspace, maybe put those in ~/CSC207
• Getting the syntax right in parts C and D took a lot of time
• Why the average problem?
  • Think about extreme cases!
  • A real issue

Java Things to Discuss

• Java is object oriented: We build and use objects
• Sometimes, we just want to be imperative and write methods - no objects really needed
  • Methods not associated with objects are called "static methods"
  • Until you build objects, everything should probably build static
• Related issue: Classes serve three basic purposes
  • Collections of static utility methods - "Utility class"
  • A repository for the main method - "Main class"
  • Templates for objects - "Template class"

ADT Design

• Sam can't speak today
• An ADT is a set of operations and values that have some common purpose
  • An array has the purpose of storing values indexed by integers
  • A list has the purpose of storing values that we can iterate through
  • A PrintWriter has the purpose of generating output
• We generally achieve that purpose through the methods
  • Arrays need methods to get the value at position i, set the value at position i, and get the length
  • PrintWriters need methods to print things and to print newlines
• We also look at the practical applications of such ADTs

Once we've done all that, we look for ways to implement the ADT

Design confilct: minimalist vs. maximalist * Scheme lists:
* Minimalist: cons, car, cdr, null, null? * Maximalist: member, trim, split, index-of, element-at, map, caaddar, length ...

Arrays

• Declare

  TYPE[] NAME
  

• Create

  new TYPE[SIZE]
  new TYPE[] { VAL1, VAL2, VAL3, ... }
  

• Access values

  NAME[INDEX]
  

• Set values

  NAME[INDEX] = VAL
  

• Get length

  NAME.length