用于2D坐标的Java哈希函数无法正常工作？

Question

我是哈希话题的新手。为了进行试验，我有一个Node类，它使用2个整数作为2D平面的坐标。但是，将节点添加到HashMap后，我无法使用键来检索它们（返回null）。下面是Node类，它同时实现Object类的hashCode（）和equals（）。这里有什么问题？函数本身吗？还是对哈希的误解？

public static class Node {
    public int x, y;
    public boolean visited;
    public ArrayList<Node> neighbours;
    public Node(int x, int y) {
        this.x = x;
        this.y = y;
        neighbours=new ArrayList<>();
    }
    public void addneighbours(Node neighbourNode)
    {
        neighbours.add(neighbourNode);
    }
    public void removeNeighbour(Node neighbourNode) {
        for (int i = 0; i < neighbours.size(); i++) {
            if (neighbours.get(i).equals(neighbourNode)) {
                neighbours.remove(i);
            }
        }
    }
    public ArrayList<Node> getNeighbours() {
        return neighbours;
    }
    public void setNeighbours(ArrayList<Node> neighbours) {
        this.neighbours = neighbours;
    }
    public int hashCode() {
        return ((x + y)*(x + y + 1)/2) + y;
    }
    public boolean equals(Node n) {
        if (n.x == x && n.y == y) {
            return true;
        } else {
            return false;
        }
    }
    public String toString() {
        return "(" + x + ", " + y + ")";
    }

}