CSC207.01 2013F, Class 11: Classes, Objects, and Interfaces

Overview

Admin

Note: I seem to be pushing you harder than I'd like on the assignments.
- Please don't spend much more than six hours on an assignment. If you're spending more than that, something is going seriously wrong.
- We'll do a demo of how not to approach these assignments.
Note: I feel like a Grinnell student. I seem to have more work than I can physically do.
- HW4 is in rough shape. We'll discuss it in the last ten minutes of class.
- I also expect to have the reading available late today.
Reading for Wednesday: Inheritance
SACNAS Ice Cream Social: Thursday, September 19th at 8:00PM in the Biology Commons
EC Opportunities
- Convocation noon, Wednesday.
- Learning from Alumni Thursday @ 2:15 Sam Tape and company.
- CS Extras Thursday @ 4:30: Kim Spasaro on Linguistics Programming
- CS Table Friday (pair programming)
- Other?

A brief introduction to objects

Core of OOP: Objects
- Group related things together
  - Data
  - Methods
- Protect from outside world
In Java, we describe objects with template classes
- Data are in fields - looks like a variable, but associated with individual objects.
public class Counter { int value; }
- Methods are methods.
- Constructors look like methods, but with a specified name and no return type
public class Counter { int value; int increment;
```
/** 
 * Create a new counter with teh value zero.
 */
public Counter() {
    this.value = 0;
    this.increment = 1;
} // Counter()


/**
 * Create a counter initialed to value.
 */
public Counter(int value) {
    this.value = value;
    this.increment = 1;
} // Counter(int)
```
} // class Counter

Sometimes you have the wrong type of object, you can cast objects.
- Throws ClassCastException
Can also ask thing instanceof Class

You are expecgted to provide some methods. (They will be available for every object, whether or not you define them.)
- String toString()
- boolean equals(Object other)
- int hashCode()
Also nice
- clone() - make a copy
- compareTo(Thing other) - neg, zero, positive