public static class FlowGraph.Edge<FlowItem extends DataFlow.Item>
This class represents an edge in the flow graph. The target of the edge
is either the head or the tail of the edge, depending on how the Edge is
used. Thus, the target field in Edges in the collection Peer.preds is the
source Peer, while the target field in Edges in the collection Peer.succs
is the destination Peer of edges.
Each Edge has an EdgeKey, which identifies when flow uses that edge in
the flow graph. See EdgeKey for more information.