Question

如何从插入地图列表中的列表中检索值？我有我的主要课程

public class Path {
private Map<Integer, List<Arc>> mapNode;
private final Arc arc;

public Path() {
    this.arc = new Arc();

    double coll[][] = {{1, 13}, {2, 21}, {21, 2}, {7, 21}, {21, 5}};

    mapNode = new HashMap();

    for (int i = 0; i < coll.length; i++) {
        if (!mapNode.containsKey((int) coll[i][0])) {
            mapNode.put((int) coll[i][0], new ArrayList());
        }
        Arc arc = new Arc();
        arc.setOrigin((int) coll[i][0]);
        arc.setDestination((int) coll[i][1]);

        mapNode.get(arc.getOrigin()).add(arc);
                mapNode.get(arc.getOrigin()).get(arc.getDestination()).getOccupancy().setInit(0);

    }
}
}

在我的地图中，我有一个Arc列表。它包含来源，目的地以及占用列表：

public class Arc {

private int origin;
private int destination;

private Occupancy occupancy;
private List <Occupancy> time_occupancy;
public Arc(){
}

public Arc(int origin, int destination){
    this.origin = origin;
    this.destination = destination;
}

public Occupancy getOccupancy() {
    return occupancy;
}

public void setOccupancy(Occupancy occupancy) {
    this.occupancy = occupancy;
}

public List<Occupancy> getTime_occupancy() {
    return time_occupancy;
}

public void setTime_occupancy(List<Occupancy> time_occupancy) {
    this.time_occupancy = time_occupancy;
}

public int getOrigin() {
    return origin;
}

public void setOrigin(int origin) {
    this.origin = origin;
}

public int getDestination() {
    return destination;
}

public void setDestination(int destination) {
    this.destination = destination;
}
}

占用是弧不可用的时间，它有两个变量：init和end。

class Occupancy {
double init;
double end;

public Occupancy(double init, double end){
    this.init = init;
    this.end = end;
}

public double getInit() {
    return init;
}

public void setInit(double init) {
    this.init = init;
}

public double getEnd() {
    return end;
}

public void setEnd(double end) {
    this.end = end;
}

}

我不能在我的入住名单中存储价值。我试过了：

mapNode.get(arc.getOrigin()).get(arc.getDestination()).getOccupancy().setInit(0);

但它不起作用。我可以在我的弧列表中获取并设置值，但我不能使用我的占用列表。

Answer 1

初始化泛型如下：

private Map<Integer, List<Arc>> mapNode;
private final Arc arc;

public Path() {
    this.arc = new Arc();

    double coll[][] = {{1, 13}, {2, 21}, {21, 2}, {7, 21}, {21, 5}};

    mapNode = new HashMap<Integer, List<Arc>>();

    for (int i = 0; i < coll.length; i++) {
        if (!mapNode.containsKey((int) coll[i][0])) {
            mapNode.put((int) coll[i][0], new ArrayList<Arc>());
        }

之后，您可以轻松索引并获取TYPED项目，而不必投射对象。

当然，您可以从以下列表中获取列表和项目：

   Map<Integer, List<Arc>> mapNode = ...;
   ...
   List<Arc> list = mapNode.get(5); //example Integer
   Arc arc = list.get(0); //index of 0

java - 在列表映射中获取和设置值

1 个答案: