Java Program to Implement the graph data structure

Example: Implement Graph Data Structure

class Graph {

  // inner class
  // to keep track of edges
  class Edge {
    int src, dest;
  }

  // number of vertices and edges
  int vertices, edges;

  // array to store all edges
  Edge[] edge;

  Graph(int vertices, int edges) {
    this.vertices = vertices;
    this.edges = edges;

    // initialize the edge array
    edge = new Edge[edges];
    for(int i = 0; i < edges; i++) {

      // each element of the edge array
      // is an object of Edge type
      edge[i] = new Edge();
    }
  }

  public static void main(String[] args) {

    // create an object of Graph class
    int noVertices = 5;
    int noEdges = 8;
    Graph g = new Graph(noVertices, noEdges);

    // create graph
    g.edge[0].src="/?originalUrl=https%3A%2F%2Fwww.programiz.com%2F1%3B%2520%2520%2520%2F%2F%2520edge%25201---2%2520%2520%2520%2520g.edge%5B0%5D.dest%2520%3D%25202%3B%2520%2520%2520%2520g.edge%5B1%5D.src%2520%3D%25201%3B%2520%2520%2520%2F%2F%2520edge%25201---3%2520%2520%2520%2520g.edge%5B1%5D.dest%2520%3D%25203%3B%2520%2520%2520%2520g.edge%5B2%5D.src%2520%3D%25201%3B%2520%2520%2520%2F%2F%2520edge%25201---4%2520%2520%2520%2520g.edge%5B2%5D.dest%2520%3D%25204%3B%2520%2520%2520%2520g.edge%5B3%5D.src%2520%3D%25202%3B%2520%2520%2520%2F%2F%2520edge%25202---4%2520%2520%2520%2520g.edge%5B3%5D.dest%2520%3D%25204%3B%2520%2520%2520%2520g.edge%5B4%5D.src%2520%3D%25202%3B%2520%2520%2520%2F%2F%2520edge%25202---5%2520%2520%2520%2520g.edge%5B4%5D.dest%2520%3D%25205%3B%2520%2520%2520%2520g.edge%5B5%5D.src%2520%3D%25203%3B%2520%2520%2520%2F%2F%2520edge%25203---4%2520%2520%2520%2520g.edge%5B5%5D.dest%2520%3D%25204%3B%2520%2520%2520%2520g.edge%5B6%5D.src%2520%3D%25203%3B%2520%2520%2520%2F%2F%2520edge%25203---5%2520%2520%2520%2520g.edge%5B6%5D.dest%2520%3D%25205%3B%2520%2520%2520%2520g.edge%5B7%5D.src%2520%3D%25204%3B%2520%2520%2520%2F%2F%2520edge%25204---5%2520%2520%2520%2520g.edge%5B7%5D.dest%2520%3D%25205%3B%2520%2520%2520%2520%2F%2F%2520print%2520graph%2520%2520%2520%2520for(int%2520i%2520%3D%25200%3B%2520i%2520%26lt%3B%2520noEdges%3B%2520i%2B%2B)%2520%257B%2520%2520%2520%2520%2520%2520System.out.println(g.edge%5Bi%5D.src%2520%2B" - " + g.edge[i].dest);
    }

  }
}

Output

1 - 2
1 - 3
1 - 4
2 - 4
2 - 5
3 - 4
3 - 5
4 - 5

In the above example, we have implemented the graph data structure in Java. To learn more about graphs, visit Graph Data Structure.