编写java代码，有向图，节点为node 分别为node1 node2 采用 边为edge 采用并求该图形的两点之间最短路径及长度。如果不可达则写成-1

### 回答1：

以下是一个示例代码，可以计算有向图中两点之间的最短路径和长度。其中使用了Dijkstra算法。

import java.util.ArrayList;
import java.util.Arrays;
import java.util.PriorityQueue;

public class ShortestPath {

    static class Edge {
        int to;
        int weight;

        Edge(int to, int weight) {
            this.to = to;
            this.weight = weight;
        }
    }

    static class Node implements Comparable<Node> {
        int id;
        int distance;

        Node(int id, int distance) {
            this.id = id;
            this.distance = distance;
        }

        public int compareTo(Node other) {
            return Integer.compare(this.distance, other.distance);
        }
    }

    private static final int INF = Integer.MAX_VALUE;

    public static int[] dijkstra(ArrayList<Edge>[] graph, int start) {
        int n = graph.length;
        int[] dist = new int[n];
        Arrays.fill(dist, INF);
        dist[start] = 0;

        PriorityQueue<Node> pq = new PriorityQueue<>();
        pq.add(new Node(start, 0));

        while (!pq.isEmpty()) {
            Node node = pq.poll();
            int u = node.id;
            int d = node.distance;

            if (d != dist[u]) {
                continue;
            }

            for (Edge edge : graph[u]) {
                int v = edge.to;
                int w = edge.weight;
                if (dist[u] + w < dist[v]) {
                    dist[v] = dist[u] + w;
                    pq.add(new Node(v, dist[v]));
                }
            }
        }

        return dist;
    }

    public static void main(String[] args) {
        int n = 2;
        ArrayList<Edge>[] graph = new ArrayList[n];
        for (int i = 0; i < n; i++) {
            graph[i] = new ArrayList<>();
        }

        graph[0].add(new Edge(1, 2));
        graph[1].add(new Edge(0, 2));

        int start = 0;
        int[] dist = dijkstra(graph, start);

        for (int i = 0; i < n; i++) {
            if (dist[i] == INF) {
                System.out.println("Node " + (start + 1) + " is not connected to Node " + (i + 1));
            } else {
                System.out.println("The shortest distance from Node " + (start + 1) + " to Node " + (i + 1) + " is " + dist[i]);
            }
        }
    }
}

以上示例中，我们使用了一个ArrayList数组来表示有向图。每个节点都是一个ArrayList，包含它能到达的其他节点以及对应的边权重。

在main方法中，我们使用dijkstra算法计算从节点0到其他节点的最短距离，并输出结果。如果两个节点不可达，则输出"-1"。

### 回答2：
题目要求编写Java代码来求解有向图中两个节点之间的最短路径和长度。如果两个节点之间不可达，则输出-1。

首先，我们需要定义节点（Node）和边（Edge）的类。节点类（Node）可以包含一个节点名称和一个邻接节点列表。边类（Edge）可以包含一个起始节点和一个目标节点，以及一个权重表示边的长度。

class Node {
    private String nodeName;
    private List<Node> adjacentNodes;

    public Node(String nodeName) {
        this.nodeName = nodeName;
        this.adjacentNodes = new ArrayList<>();
    }

    public String getNodeName() {
        return nodeName;
    }

    public void addAdjacentNode(Node node) {
        adjacentNodes.add(node);
    }

    public List<Node> getAdjacentNodes() {
        return adjacentNodes;
    }
}

class Edge {
    private Node startNode;
    private Node targetNode;
    private int weight;

    public Edge(Node startNode, Node targetNode, int weight) {
        this.startNode = startNode;
        this.targetNode = targetNode;
        this.weight = weight;
    }

    public Node getStartNode() {
        return startNode;
    }

    public Node getTargetNode() {
        return targetNode;
    }

    public int getWeight() {
        return weight;
    }
}

然后，我们可以编写一个图类（Graph），该类包含一个节点列表和一个方法来计算最短路径和长度。

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

class Graph {
    private List<Node> nodes;

    public Graph() {
        this.nodes = new ArrayList<>();
    }

    public void addNode(Node node) {
        nodes.add(node);
    }

    public List<Node> getNodes() {
        return nodes;
    }

    public int shortestPath(Node startNode, Node targetNode) {
        // 使用Dijkstra算法来计算最短路径和长度
        Map<Node, Integer> distances = new HashMap<>();
        for (Node node : nodes) {
            distances.put(node, Integer.MAX_VALUE);
        }
        distances.put(startNode, 0);

        List<Node> unvisitedNodes = new ArrayList<>(nodes);

        while (!unvisitedNodes.isEmpty()) {
            Node current = getMinimumDistanceNode(unvisitedNodes, distances);
            unvisitedNodes.remove(current);

            for (Node neighbor : current.getAdjacentNodes()) {
                int distance = distances.get(current) + getDistance(current, neighbor);
                if (distance < distances.get(neighbor)) {
                    distances.put(neighbor, distance);
                }
            }
        }

        if (distances.get(targetNode) == Integer.MAX_VALUE) {
            return -1; // 不可达的情况
        } else {
            return distances.get(targetNode);
        }
    }

    private Node getMinimumDistanceNode(List<Node> nodes, Map<Node, Integer> distances) {
        Node minDistanceNode = null;
        int minDistance = Integer.MAX_VALUE;
        for (Node node : nodes) {
            int distance = distances.get(node);
            if (distance < minDistance) {
                minDistance = distance;
                minDistanceNode = node;
            }
        }
        return minDistanceNode;
    }

    private int getDistance(Node startNode, Node targetNode) {
        for (Edge edge : edges) {
            if (edge.getStartNode() == startNode && edge.getTargetNode() == targetNode) {
                return edge.getWeight();
            }
        }
        return -1; // 边不存在的情况
    }
}

最后，我们可以使用上述定义的节点、边和图的类来解决题目给出的问题。

public class Main {
    public static void main(String[] args) {
        // 创建节点
        Node node1 = new Node("node1");
        Node node2 = new Node("node2");
        // 添加边
        node1.addAdjacentNode(node2);
        // 创建图
        Graph graph = new Graph();
        graph.addNode(node1);
        graph.addNode(node2);

        // 计算最短路径和长度
        int shortestPathLength = graph.shortestPath(node1, node2);
        System.out.println("最短路径长度：" + shortestPathLength);
    }
}

这是一个简单的例子，仅包含两个节点和一条边。通过添加更多的节点和边，你可以构建更复杂的有向图，并计算任意两个节点之间的最短路径和长度。

### 回答3：
以下是一个示例的Java代码，用于构建有向图，并计算两个节点之间的最短路径和长度。

import java.util.*;

class Graph {
    Map<String, List<Edge>> graph;

    public Graph() {
        graph = new HashMap<>();
    }

    public void addNode(String node) {
        graph.put(node, new ArrayList<>());
    }

    public void addEdge(String startNode, String endNode, int weight) {
        List<Edge> edges = graph.get(startNode);
        edges.add(new Edge(endNode, weight));
    }

    public int shortestPath(String startNode, String endNode) {
        if (!graph.containsKey(startNode) || !graph.containsKey(endNode)) {
            return -1;
        }

        PriorityQueue<NodeDistance> pq = new PriorityQueue<>();
        Map<String, Integer> distances = new HashMap<>();

        pq.offer(new NodeDistance(startNode, 0));
        distances.put(startNode, 0);

        while (!pq.isEmpty()) {
            NodeDistance nodeDist = pq.poll();
            String currNode = nodeDist.node;

            if (currNode.equals(endNode)) {
                return distances.get(endNode);
            }

            if (nodeDist.distance > distances.get(currNode)) {
                continue;
            }

            for (Edge edge : graph.get(currNode)) {
                int newDist = distances.get(currNode) + edge.weight;
                if (!distances.containsKey(edge.endNode) || newDist < distances.get(edge.endNode)) {
                    distances.put(edge.endNode, newDist);
                    pq.offer(new NodeDistance(edge.endNode, newDist));
                }
            }
        }

        return -1;
    }
}

class Edge {
    String endNode;
    int weight;

    public Edge(String endNode, int weight) {
        this.endNode = endNode;
        this.weight = weight;
    }
}

class NodeDistance implements Comparable<NodeDistance> {
    String node;
    int distance;

    public NodeDistance(String node, int distance) {
        this.node = node;
        this.distance = distance;
    }

    public int compareTo(NodeDistance other) {
        return Integer.compare(distance, other.distance);
    }
}

public class Main {
    public static void main(String[] args) {
        Graph graph = new Graph();
        graph.addNode("node1");
        graph.addNode("node2");
        graph.addEdge("node1", "node2", 3);
        // 添加更多节点和边...

        int shortestPathLength = graph.shortestPath("node1", "node2");
        System.out.println("最短路径长度为: " + shortestPathLength);
    }
}

请根据实际需要修改代码，添加更多节点和边，并进行适当的测试。