Question

我正在尝试构建priorityQueue的比较器，该比较器从Weighter<? super Vlabel>类和Distancer<? super Vlabel>返回。

这是代码：

public static <VLabel, ELabel> List<Graph<VLabel, ELabel>.Edge> shortestPath(
            Graph<VLabel, ELabel> G,
            Graph<VLabel, ELabel>.Vertex V0,
            Graph<VLabel, ELabel>.Vertex V1,
            Distancer<? super VLabel> h, //heuristic value
            Weighter<? super VLabel> vweighter,
            Weighting<? super ELabel> eweighter) {

        Stack<Graph<VLabel, ELabel>.Vertex> closedSet
            = new Stack<Graph<VLabel, ELabel>.Vertex>();
        int initial = G.vertexSize();
        PriorityQueue<Graph<VLabel, ELabel>.Vertex> fringe
            = new PriorityQueue(initial, new Comparator<Graph<VLabel, ELabel>.Vertex>() {
                public int compare(Graph<VLabel, ELabel>.Vertex v0, Graph<VLabel, ELabel>.Vertex v1) {
                    double temp1 = vweighter.weight(v0.getLabel()) + h.dist(v0, V1);
                    double temp2 = vweighter.weight(v1.getLabel()) + h.dist(v1, V1);
                    return - (int) temp1.compareTo(temp2);
                } 
            });
    }

然而它无效，因为代码抱怨它无法在比较方法中识别vweighter和h。
顺便说一句，我不允许为最短路径设置任何参数作为最终。

Answer 1

将vweighter和h参数设为最终：

shortestPath(Graph<VLabel, ELabel> G,
             Graph<VLabel, ELabel>.Vertex V0,
             Graph<VLabel, ELabel>.Vertex V1,
             final Distancer<? super VLabel> h, //heuristic value
             final Weighter<? super VLabel> vweighter,
             Weighting<? super ELabel> eweighter) {

编辑：

如果由于某种原因不允许在参数变量上使用最终运算符，则可以重新声明它们：

final Distancer<? super VLabel> myH = h;
final Weighter<? super VLabel> myVweighter = vWeighter;

然后在比较器中使用重新声明的变量。

更新2：

如果你想创建一个实现类似接口的类，并且你想要改变函数，那么你就是这样做的了：

public class WeightComparator implements
        Comparator<Graph<VLabel, ELabel>.Vertex> {

    private Graph<VLabel, ELabel> G;
    private Graph<VLabel, ELabel>.Vertex V0;
    private Graph<VLabel, ELabel>.Vertex V1;
    private Distancer<? super VLabel> h; //heuristic value
    private Weighter<? super VLabel> vweighter;
    private Weighting<? super ELabel> eweighter;

    public WeightComparator() {

    }

    @Override
    public int compare(Graph<VLabel, ELabel>.Vertex o1, Graph<VLabel, ELabel>.Vertex o2) {
        // Your compare statement
    }

    // Getters and setters for all variables
}

在实例化时，您应该保留引用并根据需要更新变量。

比较器实现涉及多个对象java

1 个答案: