Consider Bloch's Point/ColorPoint example
from exercise 9A.
public class Point { // routine code
private int x; private int y;
public Point(int x; int y) {
this.x = x; this.y = y;
// Bloch wouldn't like a call to an overridable method here. Why not?
}
@Override public boolean equals(Object obj) { // Standard recipe
if (!(obj instanceof Point)) return false;
Point p = (Point) obj;
return p.x == x && p.y == y;
}
}
- Bloch would like to see
hashCode() overridden. Do it!
- Suppose we want to have
Point
implement the Comparable interface.
Analyze the following possibilites from the contract perspective.
As usual, try to come up with test cases where appropriate.
- Comparisons just based on the value of
x.
- Comparisons based on the sum of
x and y.
- Comparisons based first on the value of
x,
and if these match, then on the value of y.
- Why wouldn't Bloch like a call to an overridable method in the
constructor? Be concrete!