Java 链表删除某一元素

package com.linkedlist;

public class ListNode {
	public int val;
    public ListNode next;

    public ListNode(int x) {
        val = x;
    }
    
    
    
    
    public ListNode(int[] arr){

        if(arr == null || arr.length == 0)
            throw new IllegalArgumentException("arr can not be empty");

        this.val = arr[0];
        ListNode cur = this;
        for(int i = 1 ; i < arr.length ; i ++){
            cur.next = new ListNode(arr[i]);
            cur = cur.next;
        }
    }

    // 以当前节点为头结点的链表信息字符串
    @Override
    public String toString(){

        StringBuilder s = new StringBuilder();
        ListNode cur = this;
        while(cur != null){
            s.append(cur.val + "->");
            cur = cur.next;
        }
        s.append("NULL");
        return s.toString();
    }
}

package com.linkedlist;

public class Solution {
	public ListNode removeElements(ListNode head,int val){
		while(head != null && head.val == val){
			ListNode delNode = head;
			head = head.next;
			delNode.next = null;
		}
		if(head == null){
			return head;
		}
		
		ListNode prev = head;
		while (prev.next != null) {
			if (prev.next.val == val) {
				ListNode delNode = prev.next;
				prev.next = delNode.next;
				delNode.next = null;
			}else{
				prev = prev.next;
			}
		}
		
		return head;
	}
	
	
	public static void main(String[] args) {
		int[] arr = {1,2,3,4,5,6,7,8,9};
 		ListNode listNode = new ListNode(arr);
 		System.out.println(listNode);
 		
 		
 		ListNode ret = (new Solution()).removeElements(listNode, 7);
 		System.out.println(ret);
	}
}

	public ListNode removeElements(ListNode head,int val){
		//获得删除节点
		while (head != null && head.val == val) {
			head = head.next;
		}
		if (head == null) {
			return null;
		}
		
		ListNode prev = head;
		while(prev.next != null){
			if(prev.next.val == val){
				prev.next = prev.next.next;
			}else{
				prev = prev.next;
			}
		}
		return head;
	}

	public ListNode removeElements(ListNode head,int val){	
	    if(head == null)
	        return head;
	
	    head.next = removeElements(head.next, val);
	    return head.val == val ? head.next : head;
	}