@Override
    public boolean hasNext() {

        if (this.doNext == ProcessStages.ProcessParent) {
            this.next = this.treeNode;
            this.doNext = ProcessStages.ProcessChildCurNode;
            return true;
        }

        if (this.doNext == ProcessStages.ProcessChildCurNode) {
            if (childrenCurNodeIter.hasNext()) {
                TreeNode<T> childDirect = childrenCurNodeIter.next();
                childrenSubNodeIter = childDirect.iterator();
                this.doNext = ProcessStages.ProcessChildSubNode;
                return hasNext();
            }

            else {
                this.doNext = null;
                return false;
            }
        }

        if (this.doNext == ProcessStages.ProcessChildSubNode) {
            if (childrenSubNodeIter.hasNext()) {
                this.next = childrenSubNodeIter.next();
                return true;
            }
            else {
                this.next = null;
                this.doNext = ProcessStages.ProcessChildCurNode;
                return hasNext();
            }
        }

        return false;
    }