public void addNode(final NodeType node){
  Preconditions.checkNotNull(node,"Node argument can not be null");
  m_nodes.add(node);
  m_nodeToEdges.put(node,new ArrayList<EdgeType>());
}

public void addNode ( final NodeType node ) { Preconditions . checkNotNull ( node , "Node argument can not be null" ) ; m_nodes . add ( node ) ; m_nodeToEdges . put ( node , new ArrayList < EdgeType > ( ) ) ; }
adds a node to the graph .
