رابط برنامه نویسی گراف (Graph Api)

import java.util.Iterator;

public class Bag<Item> implements Iterable<Item> {

     private Node<Item> first;
     private int size;

     public Bag() {
          size = 0;
          first = null;
     }

     public boolean isEmpty() {
          return first == null;
     }

     public int size() {
          return size;
     }

     public void add(Item item) {
          Node<Item> oldfirst = first;
          first = new Node<Item>(item, oldfirst);
          size++;
     }

     public Iterator<Item> iterator() {
          return new ListIterator<Item>(first);
     }

}

public class Node<Item> {

     private Item data;
     private Node next_node;

     public Node(Item data, Node next_node) {
          this.data = data;
          this.next_node = next_node;
     }

     public Item getData() {
          return data;
     }

     public Node getNext_node() {
          return next_node;
     }



}

import java.util.Iterator;
import java.util.NoSuchElementException;

public class ListIterator<Item> implements Iterator<Item> {
     private Node<Item> current;

     public ListIterator(Node<Item> first) {
          current = first;
     }

     public boolean hasNext() {
          return current != null;
     }


     public Item next() {
          if (!hasNext())
              throw new NoSuchElementException();
          Item item = current.getData();
          current = current.getNext_node();
          return item;
     }
}

public class Graph {
     private int V;
     private int E;
     private Bag<Integer>[] adj;

     public Graph(int V) {
          if (V < 0)
              throw new IllegalArgumentException(
                        "Number of vertices must be nonnegative");
          this.V = V;
          this.E = 0;
          adj = (Bag<Integer>[]) new Bag[V];
          for (int v = 0; v < V; v++) {
              adj[v] = new Bag<Integer>();
          }
     }

     public int V() {
          return V;
     }

     public int E() {
          return E;
     }

     public void addEdge(int v, int w) {
          if (v < 0 || v >= V)
              throw new IndexOutOfBoundsException();
          if (w < 0 || w >= V)
              throw new IndexOutOfBoundsException();
          E++;
          adj[v].add(w);
          adj[w].add(v);
     }

     public Iterable<Integer> adj(int v) {
          if (v < 0 || v >= V)
              throw new IndexOutOfBoundsException();
          return adj[v];
     }


}

  public static void main(String[] args) {
          Graph g = new Graph(5);
          g.addEdge(1, 2);
          g.addEdge(1, 3);
          g.addEdge(2, 3);
          g.addEdge(0, 4);
          g.addEdge(3, 4);

          for (int v = 0; v < g.V; v++) {
              System.out.print(v+"->");
              for (int w : g.adj[v]) {
                   System.out.print(w+" ");
              }
              System.out.println();

          }

     }

  public Graph(File file) throws FileNotFoundException {

          if (file.exists()) {
              try {
                   BufferedReader buffer = new BufferedReader(new FileReader(file));
                   V = Integer.parseInt(buffer.readLine());
                   E = Integer.parseInt(buffer.readLine());

                   adj = (Bag<Integer>[]) new Bag[V];

                   for (int v = 0; v < V; v++) {
                        adj[v] = new Bag<Integer>();
                   }

                   String line;
                   while ((line = buffer.readLine()) != null) {
                        int v = Integer.parseInt(line.split(" ")[0]);
                        int w = Integer.parseInt(line.split(" ")[1]);
                        addEdge(v, w);
                   }

              } catch (FileNotFoundException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
              } catch (NumberFormatException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
              } catch (IOException e) {
                   // TODO Auto-generated catch block
                   e.printStackTrace();
              }
          }else{
              throw new FileNotFoundException();
          }

     }

 Graph graph = null;
          try {
              graph = new Graph(new File("graph.txt"));
          } catch (FileNotFoundException e) {
              // TODO Auto-generated catch block
              e.printStackTrace();
          }

          for (int v = 0; v < graph.V; v++) {
              System.out.print(v+"->");
              for (int w : graph.adj[v]) {
                   System.out.print(w+" ");
              }
              System.out.println();

          }