I try very hard, buts for now I dont know whats is wrong with my code, can somebody help please?

class Result {

private static class Graph {

     private final int size;

    private long nodes = 0;

    private final long costForRoad;

    private final long costForLibrary;

    private final int[][] cities;

    public Graph(int size, final long costForRoad, final long costForLibrary) {
        this.size = size;
        this.costForRoad = costForRoad;
        this.costForLibrary = costForLibrary;
        this.cities = new int[size][];
        for (int i = 0; i < size; i++) {
            this.cities[i] = new int[size];
        }
    }

    public void addEdge(
            final int origin,
            final int destiny
    ) {
        this.cities[origin-1][destiny-1] = 1;
        this.cities[destiny-1][origin-1] = 1;
    }

   public long calcCost() {
        long cost = 0;
        final boolean[] visited = new boolean[this.size];
        for (int i = 0; i < this.size; i++) {
            if(!visited[i]) {
                nodes = 0;
                this.dfs(i, visited);
                  if(nodes == 1) {
                    cost += nodes * costForLibrary;
                } else {
                    cost += (nodes - 1) * costForRoad + costForLibrary;
                }
            }
        }

        return cost;
    }

    private void dfs(
            final int vertex,
            final boolean[] visited
    ) {
        nodes += 1;
        visited[vertex] = true;
        for (int i = 0; i < this.cities[vertex].length; i++) {
            if(this.cities[vertex][i] == 1 && !visited[i]) {
                dfs(i, visited);
            }
        }
    }
}

/*
 * Complete the 'roadsAndLibraries' function below.
 *
 * The function is expected to return a LONG_INTEGER.
 * The function accepts following parameters:
 *  1. INTEGER n
 *  2. INTEGER c_lib
 *  3. INTEGER c_road
 *  4. 2D_INTEGER_ARRAY cities
 */

public static long roadsAndLibraries(int n, int c_lib, int c_road, List<List<Integer>> cities) {
// Write your code here
    if(c_lib < c_road) {
        return n * c_lib;
    }

    final Graph graph = new Graph(n, c_road, c_lib);
    for(List<Integer> connections : cities) {
        graph.addEdge(connections.get(0), connections.get(1));
    }
    return graph.calcCost();
}

}