graph

class Graph
{
    private final int numNodes;
    private final boolean direct;
    private final boolean weight;
    private final float[][] matrix;
    private final boolean[][] isMatrix;

    Graph(int num, boolean direct, boolean weight)
    {

        this.direct = direct;
        this.weight = weight;
        this.numNodes = num;
        matrix = new float[num][num];
        isMatrix = new boolean[num][num];
    }

    public void addEdge(int start, int end)
    {
        int addValue = 1;

        if (weight)
            addValue = 0;

        matrix[start][end] = addValue;
        isMatrix[start][end] = true;

        if (!direct)
        {
            matrix[end][start] = addValue;
            isMatrix[end][start] = true;
        }
    }

    public void addEdge(int start, int end, float the_weight)
    {
        float addValue = the_weight;

        if (!weight)
            addValue = 1;

        matrix[start][end] = addValue;
        isMatrix[start][end] = true;

        if (!direct)
        {
            matrix[end][start] = addValue;
            isMatrix[end][start] = true;
        }
    }

    public void printMatrix()
    {
        for (int i = 0; i < numNodes; i++)
        {
            for (int j = 0; j < numNodes; j++)
            {
                if (isMatrix[i][j])
                    System.out.format("%8s", matrix[i][j]);
                else
                    System.out.format("%8s", "/  ");
            }
            System.out.println();
        }
    }

    public void printEdges()
    {
        for (int i = 0; i < numNodes; i++)
        {
            System.out.print("Node " + i + " is connected to: ");
            for (int j = 0; j < numNodes; j++)
            {
                if (isMatrix[i][j])
                    System.out.print(j + " ");
            }
            System.out.println();
        }
    }

    public boolean hasEdge(int start, int end)
    {
        return isMatrix[start][end];
    }
}

public class Main
{
    public static void main(String[] args)
    {
        Graph graph = new Graph(6, false, true);

        graph.addEdge(0, 1, 19);
        graph.addEdge(0, 2, 10);
        graph.addEdge(0, 3, 7);
        graph.addEdge(0, 4, 2);
        graph.addEdge(0, 5, 11);
        graph.addEdge(1, 2, 3);
        graph.addEdge(1, 3);
        graph.addEdge(1, 4);
        graph.addEdge(2, 3);
        graph.addEdge(3, 4);
        graph.addEdge(4, 5);

        graph.printMatrix();

        System.out.println();
        System.out.println();

        graph.printEdges();

        System.out.println();
        System.out.println("Does an edge from 1 to 5 exist?");

        if (graph.hasEdge(0,1))
            System.out.println("Yes");
        else
            System.out.println("No");
    }
}