code: public void addNode(Node node) {
  
  		long nId = node.getId();
  		
  		if (this.containsNode(nId))
  			throw new DuplicatedNodeException(nId);
  		int index = nextNodeId++;
  		nodeIdMapping.put(nId, index);
  
  		int aliveIndex = index >> 5;
  		int aliveSubIndex = index & 31;
  
  		if (aliveIndex >= aliveNodes.size())
  			aliveNodes.add(0);
  
  		aliveNodes.set(aliveIndex, aliveNodes.get(aliveIndex) | (byte)(1 << aliveSubIndex));
  
  		adjacency.add(new IntHashSet[] {new IntHashSet(), new IntHashSet()});
  
  		nodes.add(node);
  		numberOfNodes++;
  	}
docs: Add a new node into the graph.
  @param node the node that will be added.