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 null;
        }

        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;
    }
}

class Solution {
    public ListNode removeElements(ListNode head, int val) {

        ListNode dummyHead = new ListNode(0);
        dummyHead.next = head;

        ListNode prev = dummyHead;

        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 dummyHead.next;
    }
}

数组长度为0和数组为null区别

数组长度为0和数组为null
java中数组为空和数组长度为0的区别