无头单向非循环链表实现（java）

public class IndexException extends RuntimeException{
    public IndexException() {

    }
    public IndexException(String msg) {
        super(msg);
    }
}

public class MySingleList {
    static class ListNode {
        public int val;
        public ListNode next;
        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;//null 链表的头结点

    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        node.next = this.head;
        this.head = node;
    };
    //尾插法
    public void addLast(int data){
        ListNode node = new ListNode(data);
        if (head == null) {
            head = node;
        }else {
            ListNode cur = head;
            while(cur .next != null) {
                cur = cur.next;
            }
            cur.next = node;
        }
    };
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if (index < 0 || index > size()) {
            throw new IndexException("index不合法：" + index);
        }
        ListNode node = new ListNode(data);
        if(head == null) {
            head = node;
            return;
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        //中间插入
        ListNode cur = head;
        int count = 0;
        while (count != index -1) {
            cur = cur.next;
            count++;
        }
        node.next = cur.next;
        cur.next = node;
    };
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = head;
        while (cur != null) {
            if (cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    };
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        if (head == null) {
            return;
        }
        if (head.val == key) {
            head = head.next;
            return;
        }
        ListNode cur = head;
        while (cur.next != null) {
            if (cur.next.val ==key) {
                cur.next = cur.next.next;
            }else {
                cur = cur.next;
            }
        }
    };
    //删除所有值为key的节点
    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;
        }

    };
    //得到单链表的长度
    public int size(){
        int count = 0;
        ListNode cur = head;
        while(cur != null) {
            cur = cur.next;
            count++;
        }
        return count;
    };
    //遍历链表
    public void display(){
        ListNode cur = head;
        while (cur != null) {
            System.out.println(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    };
    //删除链表
    public void clear(){
        head = null;
    };
}