1/14/2009
1
Class Design
CS 3331
Question
public class StudentBody1 {
private ArrayList students;
/* … */
public void addAll(ArrayList students) { /* … */ }
}
public class StudentBody2 {
private List students;
/* … */
public void addAll(List students) { /* … */ }
}
Design Guidelines
•G1: Avoid public fields
•G2: Make public interfaces complete
•G3: Separate interface from implementation
Canonical Form of Classes
// E.g., what will be printed?
List points = new LinkedList();
points.add(new Point(10, 20));
If (points.contains(new Point(10, 20))) {
System.out.println(“Found!”);
} else {
System.out.println(“Not found!”);
}
Canonical Form (Cont.)
•Canonical forms of public classes
–String representation
–No-argument constructor
–Object equality
–Cloning
–Serialization
Equality
•Identity equality vs. value quality
“==“ vs. equals()
“==“ implies equals()
Is “p1 == p2” ?
Is “p1.equals(p2)” ?
Is “p1 == p3” ?
Is “p1.equals(p3)” ?
: Point
x = 10
y = 20
p1:
: Point
x = 10
y = 20
p2:
p3:
Point p1 = new Point(10, 20);
Point p2 = new Point(10, 20);
Point p3 = p1;
