Correct equals in Point.java

src/edu/caltech/cs2/lab09/Point.java

      */
     @Override
     public boolean equals(Point point) {
-        if (point == null) return false;
-        int x = point.x;
-        int y = point.y;
+        if (!(point instanceof Point)) {
+            return false;
+        }
+        Point p = (Point) point;
+        int x = p.x;
+        int y = p.y;
         return (this.x == x && this.y == y);
     }
 }