Java抽象类泛型方法参数

Question

I'm running into a problem with java abstract classes and generic functions. The implementation is a node class in a graph for Dijkstra's algorithm.

public abstract class Node {

    float distance;
    Node parent;

    public void relax(Node parent, Edge edge, PriorityQueue<? extends Node> priorityQueue) {
        if (this.distance > parent.distance + edge.weight){
            this.distance = parent.distance + edge.weight;
            this.parent = parent;
            priorityQueue.remove(this);
            priorityQueue.add(this);
        }
    }
}

The problem is the line:

priorityQueue.add(this);

Because this references the Node class (which is abstract) it cannot be added to the priority queue and should in fact be of type ? (the subclass of node) denoted in ? extends Node . How to I reference this subclass type?

Thanks in advance.

Answer 1

I'm not sure what you want to achieve. I see two variants. Either you will use one type of subclass of a node and then you can write something like:

public <T extends Node> void relax(T parent, Edge edge, PriorityQueue<T> priorityQueue) {
    if (this.distance > parent.distance + edge.weight){
        this.distance = parent.distance + edge.weight;
        this.parent = parent;
        priorityQueue.remove(this);
        priorityQueue.add((T) this);
    }
}

Or you want to just use different types of nodes and mix and match them but then the type for queue will be just PriorityQueue<Node> .