import java.util.*;

/**
 * A base to help implement a directed graph
 */
public class Graph<V,E extends Edge<V>> implements GraphInterface<V,E> {


	/**
	 * Creates an empty graph.
	 */
	public Graph()
	{
	}

	/**
	 * Creates a graph with pre-defined vertices.
	 *
	 * @param vertices
	 *            A list of the vertices in the graph.
	 * @throws NullPointerException
	 *             If vertices is null, or contains null items
	 */
	public Graph (Collection<? extends V> vertices)
	{
	}

	/**
	 * Creates a graph with pre-defined edges and vertices.
	 *
	 * @param vertices
	 *            A list of the vertices in the graph.
	 * @param edges
	 * 			  A list of edges for the graph.
	 * @throws IllegalArgumentException if edges contains invalid edges.
	 * @throws NullPointerException
	 *             If vertices or edges is null, or either contain null items
	 */
	public Graph (Collection<? extends V> vertices, Collection<? extends E> edges)
	{
	}

	/**
	 * Copy Constructor
	 *
	 * @param g
	 *            A graph to copy
	 * @throws IllegalArgumentException if g violates Graph invariants by
	 *            returning illegal edges in its outgoingEdge methods
	 * @throws NullPointerException
	 *             If g is null, or g's methods violates Graph invariants
	 *             by returning null items in verticies or outgoingEdges
	 */
	public Graph (GraphInterface <V, E> g)
	{
	}


	public boolean addVertex(V vertex)
	{
		return false;
	}

	public boolean addVertices(Collection<? extends V> vertices)
	{
		return false;
	}

	public boolean addEdge (E e)
	{
		return false;
	}

	public boolean addEdges (Collection<? extends E> edges)
	{
		return false;
	}

	public boolean removeEdge (V src, V dest)
	{	
		return false;
	}

	public void clearEdges ()
	{
		
	}

    public Set<V> vertices ()
	{
		return null;
    }

	public E connected (V i, V j)
	{
		return null;
	}

	public Set<V> neighbors (V vertex)
	{
		return null;
	}

	public Collection<E> outgoingEdges (V vertex)
	{
		return null;
	}
}