Held: Monday, 8 September 2014

Back to Outline 05 - Unit Testing. On to Outline 07 - Classes and Objects, Revisited.

Summary

We continue our exploration of object-oriented programming by examining Java's approach to objects, the building blocks of object-oriented programming.

Related Pages

• Reading: Writing Your Own Classes
• Reading: Standard Objects Methods
• Lab: Writing Your Own Classes
• EBoard 6 (Source 6) (HTML 6)

Overview

• A brief introduction to objects.
• An exercise: Counters.

Administrivia

• I brought you food. I hope you brought me surveys.
• A few of you have asked that we use IntelliJ instead of Eclipse. If you really want me to switch, we have to figure out the following:
  • I'll need you to build me a code preferences file that matches my code conventions. (I'm willing to vary a bit, but not too much.)
  • You need to find a way to make sure that it is a reasonable user of our file system.

Upcoming Work

• HW 3 due Tuesday.
  • About half of you haven't done the prologue, which worries me
  • Worries about part C? ("the wording is confusing")
  • Finding methods: Eclipse and the API pages shuld be useful
• Daily lab writeup: http://bit.ly/207writeup
• Reading for Tuesday:
  • Arrays in Java

Extra Credit Opportunities

• I haven't seen many responses yet. EC is a good and easy way to earn a few more points for the course.

Academic

• Convo next Wednesday at noon. "Limiting Armed Drone Proliferation" by Micah Zenko, the Douglas Dillon fellow in the Center for Preventive Action at the Council on Foreign Relations and vice chair of the World Economic Forum Global Agenda Council on Terrorism.
  • Sam's comments on the value of convo
• Any other event in the Rosenfield Drones program.
• CS Extra, Thursday, September 11: Ajuna Kyaruzi '17 on being a SysAdmin
• CS Table, Friday, September 12: Socially-Assistive Robots Help Children with Autism

Peer Support

• Men's Soccer (?)

Miscellaneous

• Second-year students get extra credit for doing the second-year science retreat on Sept. 20.

A Brief Introduction to Objects

• The core of object-oriented programming.
• Key idea one: Encapsulation.
  • Group methods and data.
  • Protect data (and some methods).
• In Java, we use template classes to build objects.
• The template specifies
  • The data (fields).
  • The methods.
  • The constructors.
• Fields look like variable declarations.
• Methods look like methods.
• Constructors look like methods with the same name as the class.

Side Notes

• You can cast objects.
  
  • You'll get a ClassCastException if Java can't convert them.
• The instanceof operation lets you determine whether an object can be cast.

Standard Object Methods

• Java classes are expected to have a few standard methods.
  • toString() - convert to a string
  • equals() - determine if this object equals another object
  • hashCode() - convert to a relatively unique integer
• There are also a few common methods
  • clone() - make a copy
  • compareTo() - compare to another object of the same type

Exercise: Counters

• We'll try to build counter objects.