/guava/guava/src/com/google/common/graph/DirectedGraphConnections.java
previousSuccessor = false;
previousSuccessor = null;
@Override @CheckForNull public V addSuccessor(N node, V value) { Object previousValue = adjacentNodeValues.put(node, value); Object previousSuccessor; if (previousValue == null) { <extra_id_0> } else if (previousValue instanceof PredAndSucc) { adjacentNodeValues.put(node, new PredAndSucc(value)); previousSuccessor = ((PredAndSucc) previousValue).successorValue; } else if (previousValue == PRED) { adjacentNodeValues.put(node, new PredAndSucc(value)); previousSuccessor = null;