Graph.java

Graph.java

package graphs;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Graph {

	private int V;
	private int E = 0;
	private List<Integer>[] adj;

	@SuppressWarnings("unchecked")
	public Graph(int V_) {
		this.V = V_;
		adj = new List[V_];
		for (int i = 0; i < adj.length; i++) {
			adj[i] = new ArrayList<Integer>();
		}
	}

	public List<Integer> adj(int v) {
		return adj[v];
	}

	public void addDirectedEdge(int from, int to) {
		if (!adj[from].contains(to)) {
			E++;
			adj[from].add(to);
		}
	}

	public void addUndirectedEdge(int from, int to) {
		addDirectedEdge(from, to);
		addDirectedEdge(to, from);
	}

	public int V() {
		return V;
	}

	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append("Graph with V = " + V + " , E = " + E + "\n");
		for (int i = 0; i < this.V(); i++) {
			sb.append(i + ": ");
			sb.append(adj[i]);
			sb.append("\n");
		}

		return new String(sb);
	}

	private class VertexIterator implements Iterator<Integer> {
		private int vertex = 0;

		@Override
		public boolean hasNext() {
			return (vertex < Graph.this.V);
		}

		@Override
		public Integer next() {
			int current = vertex;
			vertex++;
			return current;
		}

		@Override
		public void remove() {
			// TODO Auto-generated method stub

		}

	}

	public Iterator<Integer> iterateVertices() {
		return new VertexIterator();
	}

	public Iterator<Integer> iterateEdges(int v) {
		return this.adj[v].iterator();
	}

	public static void main(String[] args) {
		int V = 2;
		Graph g = new Graph(V);

		System.out.println(g);

	}
}