思路没什么特别的，就是换个java的写法

import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int N = 0x3f3f3f3f;
        int n = scanner.nextInt(), m = scanner.nextInt();

        Map<Integer, List<PII>> g = new HashMap<>();

        int[] distance = new int[n + 1];
        boolean[] state = new boolean[n + 1];
        // 初始化距离数组
        Arrays.fill(distance, N);
        distance[1] = 0;

        // 构造邻接表
        while (m-- > 0) {
            int x = scanner.nextInt(), y = scanner.nextInt(), w = scanner.nextInt();
            if(!g.containsKey(x)) g.put(x, new ArrayList<>());
            g.get(x).add(new PII(w,y));
        }
        dijkstra(n, g, state, distance);
        if (distance[n] == N)
            System.out.println(-1);
        else
            System.out.println(distance[n]);
        scanner.close();
    }

    private static void dijkstra(int n, Map<Integer, List<PII>> g, boolean[] state, int[] distance) {

        PriorityQueue<PII> heap = new PriorityQueue<>();
        heap.offer(new PII(0, 1));

        while (!heap.isEmpty()) {
            PII top = heap.poll();
            if(state[top.index]) continue;
            state[top.index] = true;
            List<PII> list =  g.get(top.index);
            if (list == null)
                continue;
            for (PII item : list) {
                if (!state[item.index] && distance[item.index] > top.weiget + item.weiget) {
                    distance[item.index] = top.weiget + item.weiget;
                    heap.offer(new PII(distance[item.index], item.index));
                }
            }
        }
    }

    // 邻接表元素
    static class PII implements Comparable<PII> {
        int weiget;
        int index;

        /**
         * @param weiget 权重
         * @param index  结点编号
         */
        public PII(int weiget, int index) {
            this.weiget = weiget;
            this.index = index;
        }

        @Override
        public int compareTo(PII o) {
            // 重写比较器，即指定PII类在排序比较大小时的规则，方便使用优先队列
            // 比较器要求返回一个整数（正数代表o1>o2），我们想按照权重来排序，只需返回两者权重的差值即可
            return this.weiget - o.weiget;
        }
    }
}