I have a simple custom Point class as follows and I would like to know if my hashCode implemention could be improved or if this is the best it's going to get.
public class Point
{
private final int x, 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)
{
if (this == other)
return true;
if (!(other instanceof Point))
return false;
Point otherPoint = (Point) other;
return otherPoint.x == x && otherPoint.y == y;
}
@Override
public int hashCode()
{
return (Integer.toString(x) + "," + Integer.toString(y)).hashCode();
}
}
Please do not use Strings. There's a lot of theory behind this and several implementations (division method, multiplication one, etc...). If you have about a hour you can watch this MIT-Class
This being said, here is what Netbeans 7.1 suggests:
@Override
public int hashCode() {
int hash = 7;
hash = 71 * hash + this.x;
hash = 71 * hash + this.y;
return hash;
}
October 2015 Edit
I started using IntelliJ a while back, I live happier now. This is what its automatic hashCode generation produces. It's a little less verbose. Note the use of prime numbers as well.
@Override
public int hashCode() {
int result = x;
result = 31 * result + y;
return result;
}