public class GraphAdjacentMatrix {

    private boolean adjMatrix[][];
    private int numVertices;

    public GraphAdjacentMatrix(int numVertices) {
        this.numVertices = numVertices;
        adjMatrix = new boolean[numVertices][numVertices];
    }

    public void setEdge(int i, int j) {
        adjMatrix[i][j] = true;
        adjMatrix[j][i] = true;
    }

    public void delEdge(int i, int j) {
        adjMatrix[i][j] = false;
        adjMatrix[j][i] = false;
    }

    public boolean isEdge(int i, int j) {
        return adjMatrix[i][j];
    }

    public int first(int v1){
        boolean[] ary = this.adjMatrix[v1];
        int firstNeighborIndex = this.numVertices; // return n if none
        for (int i = 0; i < ary.length; i++) {
            if (ary[i] != false){
                firstNeighborIndex = i;
                break;
            }
        }
        return firstNeighborIndex;
    }

    public int next(int v1, int v2){
        boolean[] ary = this.adjMatrix[v1];
        int nextNeighborIndex = this.numVertices; // return n if none
        for (int i = v2 + 1; i < ary.length; i++) {
            if (ary[i] != false){
                nextNeighborIndex = i;
                break;
            }
        }
        return nextNeighborIndex;
    }

    public String toString() {
        StringBuilder s = new StringBuilder();
        for (int i = 0; i < numVertices; i++) {
            s.append(i + ": ");
            for (boolean j : adjMatrix[i]) {
                s.append((j?1:0) + " ");
            }
            s.append("\n");
        }
        return s.toString();
    }

    public static void main(String[] args) {
        GraphAdjacentMatrix gam = new GraphAdjacentMatrix(5);
        boolean isEdge;
        gam.setEdge(0, 1);
        isEdge = gam.isEdge(0, 1);
        gam.delEdge(0, 1);
        isEdge = gam.isEdge(0, 1);

        gam.setEdge(0, 1);
        gam.setEdge(0, 2);
        gam.setEdge(0, 4);

        int nextNeighbor;
        nextNeighbor = gam.first(0);
        nextNeighbor = gam.next(0, nextNeighbor);
        nextNeighbor = gam.next(0, nextNeighbor);
        nextNeighbor = gam.next(0, nextNeighbor);

        System.out.print(gam.toString());
        System.out.println();
    }

}