????????2????????equals????????????hashCode?????

??????????????????????Point?????p1??p2a?????????????????????true??????????????????????????HashSet.contains()?????в???????п?????????false??????

Point p1 = new Point(1?? 2);
Point p2 = new Point(1?? 2);

HashSet coll = new HashSet();
coll.add(p1);

System.out.println(coll.contains(p2)); // ??? false (?п???)

???????????????????????false??????????з???ture????????????????????true???????????????????????????????????????????????в????????????????????????????Point??????equals????????hashCode??

??????????????????????????HashSet??????ζ???????е??????????????????????”???? hash buckets”?С?contains?????????????????????в???????????е?????????????????????б????????????????Point???汾???????equals????????????????????????hashCode??????hashCode?????Object???????汾????????????????????????任??????p1??p2??????????????????????????????????????????????????????????????????м???????????????????в????????С?contains???????????p2?????????????е????????????????????￡?p1????????????????У?????p2????????p1??????????p2??p2???????????????????У???????????￡?contains?????true???

?????????Point????????????????????Υ???????Object???????hashCode?????塣

??????????????????equals(Object)???????????????????????????????hashCode??????ò???????????

????????????Java?У?hashCode??equals???????????????????????????hashCode???????????equals?????????????????????Point????????????????hashCode???????????????????塣

public class Point {

    private final int x;
    private final int y;

    public Point(int x?? int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    @Override public boolean equals(Object other) {
        boolean result = false;
        if (other instanceof Point) {
            Point that = (Point) other;
            result = (this.getX() == that.getX() && this.getY() == that.getY());
        }
        return result;
    }

    @Override public int hashCode() {
        return (41 * (41 + getX()) + getY());
    }

}

?????????hashCode????????????x????????41??????????41????????????y???????????????????????????????????????С??????????????????(?????????????????????)??

????????hashCode?????????????????????Point?????????????????????????????????????????????????

????δ?????......