private static int verifyProperty5Helper(Node<?> n, int blackCount, int pathBlackCount) {
    if (isBlack(n)) {
      blackCount++;
    }
    if (n == null) {
      if (pathBlackCount == -1) {
        pathBlackCount = blackCount;
      }
      else {
        assert blackCount == pathBlackCount;
      }
      return pathBlackCount;
    }
    pathBlackCount = verifyProperty5Helper(n.getLeft(), blackCount, pathBlackCount);
    pathBlackCount = verifyProperty5Helper(n.getRight(), blackCount, pathBlackCount);

    return pathBlackCount;
  }
private static int verifyProperty5Helper(Node<?> n, int blackCount, int pathBlackCount)