Code

Rectangle2D rect1 = e.getNode().getBounds();
ArrayList<DiagramNode> nodesAtSameX = new ArrayList<DiagramNode>();
for (DiagramNode node : diagram.getNodes())
{
	if (node == e.getNode())
		continue;
	Rectangle2D.Float rect2 = node.getBounds();
	if (rect2.getMinX() > rect1.getMaxX() ||
		rect1.getMinX() > rect2.getMaxX())
		continue;
	nodesAtSameX.add(node);
}
boolean intersects = false;
do
{
	intersects = false;
	for (DiagramNode node : nodesAtSameX)
	{
		if (DiagramNode.nodesIntersect(node, e.getNode()))
		{
			e.getNode().moveTo(
				e.getNode().getBounds().x,
				(float)node.getBounds().getMaxY() + 5);
			intersects = true;
			break;
		}
	}
}
while (intersects);