单链表的逆转

package 翻转链表;// Definition for ListNode.class ListNode {    int val;    ListNode next;    ListNode(int val) {        this.val = val;        this.next = null;    }}public class Solution {    /**     * @param head:     *            The head of linked list.     * @return: The new head of reversed linked list.     */    public ListNode reverse(ListNode head) {        // write your code here        if (head == null) {            return head;        }        ListNode pre = null,next =null;        while(true){            if(head != null){                next = head.next;                head.next = pre;                pre = head;                head = next;            } else {                break;            }        }        return pre;    }    public static void main(String[] args){        ListNode root = new ListNode(1);        ListNode one = new ListNode(2);        ListNode two = new ListNode(3);        root.next = one;        one.next = two;        print(new Solution().reverse(root));    }    private static void print(ListNode root) {        if(root == null){            return ;        }         System.out.println(root.val+ " ");        print(root.next);    }}