GraphShow.java

package Graphs;

 class Graph {

    private int numOfNodes;
    private boolean directed;
    private boolean weighted;
    private float[][] matrix;
    private boolean[][] isSetMatrix;

    Graph(int numOfNodes, boolean directed, boolean weighted) {
        this.directed = directed;
        this.weighted = weighted;
        this.numOfNodes = numOfNodes;

        matrix = new float[numOfNodes][numOfNodes];
        isSetMatrix = new boolean[numOfNodes][numOfNodes];
    }
     public void addEdge(int source, int destination, float weight) {

         float valueToAdd = weight;

         if (!weighted) {
             valueToAdd = 1;
         }

         matrix[source][destination] = valueToAdd;
         isSetMatrix[source][destination] = true;

         if (!directed) {
             matrix[destination][source] = valueToAdd;
             isSetMatrix[destination][source] = true;
         }
     }
     public void addEdge(int source, int destination) {

         int valueToAdd = 1;

         if (weighted) {
             valueToAdd = 0;
         }

         matrix[source][destination] = valueToAdd;
         isSetMatrix[source][destination] = true;

         if (!directed) {
             matrix[destination][source] = valueToAdd;
             isSetMatrix[destination][source] = true;
         }
     }
     public void printMatrix() {
         for (int i = 0; i < numOfNodes; i++) {
             for (int j = 0; j < numOfNodes; j++) {
                 if (isSetMatrix[i][j])
                     System.out.format("%8s", String.valueOf(matrix[i][j]));
                 else System.out.format("%8s", "/  ");
             }
             System.out.println();
         }
     }
     public void printEdges() {
         for (int i = 0; i < numOfNodes; i++) {
             System.out.print("Node " + i + " is connected to: ");
             for (int j = 0; j < numOfNodes; j++) {
                 if (isSetMatrix[i][j]) {
                     System.out.print(j + " ");
                 }
             }
             System.out.println();
         }
     }
     public boolean hasEdge(int source, int destination) {
         return isSetMatrix[source][destination];
     }

     public Float getEdgeValue(int source, int destination) {
         if (!weighted || !isSetMatrix[source][destination])
             return null;
         return matrix[source][destination];
     }
}
public class GraphShow {
    public static void main(String[] args) {
        Graph graph = new Graph(5, false, true);

        graph.addEdge(0, 2, 19);
        graph.addEdge(0, 3, -2);
        graph.addEdge(1, 2, 3);
        graph.addEdge(1, 3); // The default weight is 0 if weighted == true
        graph.addEdge(1, 4);
        graph.addEdge(2, 3);
        graph.addEdge(3, 4);

        graph.printMatrix();

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

        graph.printEdges();

        System.out.println();
        System.out.println("Does an edge from 1 to 0 exist?");
        if (graph.hasEdge(0,1)) {
            System.out.println("Yes");
        }
        else System.out.println("No");
    }
}