package edu.uci.ics.jung.graph.util;
   
   /**
    * A class that is used to link together a graph element and a specific graph.
    * Provides appropriate implementations of <code>hashCode</code> and <code>equals</code>.
    */
   public class Context<G,E> 
   {
   	@SuppressWarnings("rawtypes")
  	private static Context instance = new Context();
  	
  	/**
  	 * The graph element which defines this context.
  	 */
  	public G graph;
  
  	/**
  	 * The edge element which defines this context.
  	 */
  	public E element;
  	
  	/**
  	 * @param <G> the graph type
  	 * @param <E> the element type
  	 * @param graph the graph for which the instance is created
  	 * @param element the element for which the instance is created
  	 * @return an instance of this type for the specified graph and element
  	 */
  	@SuppressWarnings("unchecked")
  	public static <G,E> Context<G,E> getInstance(G graph, E element) {
  		instance.graph = graph;
  		instance.element = element;
  		return instance;
  	}
  	
  	@Override
  	public int hashCode() {
  		return graph.hashCode() ^ element.hashCode();
  	}
  	
  	@SuppressWarnings("rawtypes")
  	@Override
      public boolean equals(Object o) {
          if (!(o instanceof Context))
              return false;
          Context context = (Context) o;
          return context.graph.equals(graph) && context.element.equals(element);
      }
  }