链表的几种常见方法

public class MySinglelist {
    class  ListNode{
        public int val;
        public ListNode next;
        public ListNode(int val){
            this.val = val;
        }
    }
    public ListNode head;
    public void creatlink(){
        ListNode listNode1 = new ListNode(12);
        ListNode listNode2 = new ListNode(45);
        ListNode listNode3 = new ListNode(23);
        ListNode listNode4 = new ListNode(90);
        listNode1.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        head = listNode1;
    }

  public void display3(ListNode phead){
        if (phead == null){
            return;
        }
        if (phead.next == null){
            System.out.println(phead.val + "");
            return;
        }
        display3(phead.next);
        System.out.println(phead.val + "");
    }

public void display4(){
        Stack<ListNode>stack = new Stack<>();
        ListNode cur = head;
        while (cur!=null){
            stack.push(cur);
            cur = cur.next;
        }
        while (!stack.isEmpty()) {
            ListNode top = stack.pop();
            System.out.print(top.val+" ");
        }
        System.out.println();
    }

public void display(){
        ListNode cur = head;
        while(cur!=null){
            System.out.println(cur.val + "");
            cur = cur.next;
        }
        System.out.println();
    }

public boolean contains(int key){
        ListNode cur = head;
        while(cur!=null){
            if (cur.val ==key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

public int size(){
        int count = 0;
        ListNode cur = head;
        while (cur!=null){
            count++;
            cur = cur.next;
        }
        return count;
    }

public void addFirst(int data){
        ListNode listNode = new ListNode(data);
        listNode.next = head;
        head = listNode;
    }

public void addLast(int data){
        ListNode listNode = new ListNode(data);
        if (head == null){
            head = listNode;
            return;
        }
        ListNode cur = head;
        while (cur.next!=null){
            cur = cur.next;
        }
        cur.next = listNode;
    }

 public void removeAllKey(int key){
        if(head == null) {
            return;
        }
        ListNode prev = head;
        ListNode cur = head.next;
        while (cur != null) {
            if(cur.val == key) {
                prev.next = cur.next;
                cur = cur.next;
            }else {
                prev = cur;
                cur = cur.next;
            }
        }
        if(head.val == key) {
            head = head.next;
        }
    }
}