java - 如何为仅包含对下一个节点的引用的节点实现HashCode()？

Question

public class Node {
    private Node nextNode;

    @Override
    public int hashCode() {
        //How to implement this?
        //Because you just have a attribute which is a reference.
        //I think the attribute is almost useless, because if you use the HashCode of the attribute, you will finally fall into a useless loop.
        //Thus, I think you should find a way to represent the HashCode of reference (instance) itself.
    }
}

根据代码中的注释，我的问题实际上是如何唯一标识引用本身，例如C中的地址。

Answer 1

如果您希望Node的哈希码表示其自己的引用(即，如果您不覆盖equals(Object))，则根本不需要覆盖hashCode()。

如果您希望Node的哈希码表示其nextNode的引用，即equals(Object)看起来像这样:

@Override
public boolean equals(Object that)
{
    return ((that instanceof Node) && (nextNode == ((Node) that).nextNode));
}

—然后可以使用the JDK's System.identityHashCode(Object) utility method:

@Override
public int hashCode()
{
    return System.identityHashCode(nextNode);
}