/** 遍历一棵树,层次遍历。 */ public void traverse() { if (id == null) { return; } // 执行遍历后动作。 if (childList == null || childList.isEmpty()) return; int childNumber = childList.size(); for (int i = 0; i < childNumber; i++) { TreeNode child = childList.get(i); child.traverse(); } }