Collecting Objects - Beginning Java 7 - page 500

Point p = (Point) o;
return p.x == x && p.y == y;

}
@Override
public int hashCode()
{

int hashCode = 19;
int hc = x;
hashCode = hashCode*31+hc;
hc = y;
hashCode = hashCode*31+hc;
return hc;

}
public static void main(String[] args)
{

Point p1 = new Point(10, 20);
Point p2 = new Point(20, 30);
Point p3 = new Point(10, 20);
// Test reflexivity
System.out.println(p1.equals(p1)); // Output: true
// Test symmetry
System.out.println(p1.equals(p2)); // Output: false
System.out.println(p2.equals(p1)); // Output: false
// Test transitivity
System.out.println(p2.equals(p3)); // Output: false
System.out.println(p1.equals(p3)); // Output: true
// Test nullability
System.out.println(p1.equals(null)); // Output:

false

// Extra test to further prove the instanceof oper-
ator's usefulness.
System.out.println(p1.equals("abc")); // Output:

false

Map<Point, String> map = new HashMap<Point,

String>();
map.put(p1, "first point");