populating-next-right-pointers-in-each-node Java code

Given a binary tree
struct TreeLinkNode {
TreeLinkNode *left;
TreeLinkNode *right;
TreeLinkNode *next;
}
Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set toNULL.
Initially, all next pointers are set toNULL.
Note:
You may only use constant extra space.
You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).
For example,
Given the following perfect binary tree,
1
/ \
2 3
/ \ / \
4 5 6 7
After calling your function, the tree should look like:
1 -> NULL
/ \
2 -> 3 -> NULL
/ \ / \
4->5->6->7 -> NULL

/** * Definition for binary tree with next pointer. * public class TreeLinkNode { *     int val; *     TreeLinkNode left, right, next; *     TreeLinkNode(int x) { val = x; } * } */public class Solution {/*     * 解析：     * 1.对每层进行处理     * 2.从左边开始处理     * 3.当前节点的左孩子指向右孩子，右孩子指向当前节点的兄弟节点的左孩子，通过当前节点的next获得兄弟节点的左孩子     */    public void connect(TreeLinkNode root) {        TreeLinkNode level_start=root;//level_start用于保存每层开始时的头指针（指向每层最左边的孩子）        while(level_start!=null){            TreeLinkNode cur=level_start;//在遍历当前层所有节点时，cur与用于临时保存            while(cur!=null){                if(cur.left!=null)cur.left.next=cur.right;//当前节点的左孩子指向右孩子                if(cur.right!=null && cur.next!=null)cur.right.next=cur.next.left;//右孩子指向当前节点的兄弟节点的左孩子                cur=cur.next;//右移到兄弟节点            }            level_start=level_start.left;//处理下一层        }    }}