DirectedMultiNetworkConnections.java 文件源码

private Multiset<N> predecessorsMultiset() {
  Multiset<N> predecessors = getReference(predecessorsReference);
  if (predecessors == null) {
    predecessors = HashMultiset.create(inEdgeMap.values());
    predecessorsReference = new SoftReference<Multiset<N>>(predecessors);
  }
  return predecessors;
}