链表模拟栈

//链表操作
class LinkedListStack {
    private LinkedList head = new LinkedList(-1);
    //判断栈空
    public boolean isEmpty() {
        return head.next == null;
    }

    public void push(int num) {
        if (isEmpty()) {
            head.next = new LinkedList(num);
        } else {
            LinkedList newNum = new LinkedList(num);
            newNum.next = head.next;
            head.next = newNum;
        }
    }

    public int pop() {
        if (isEmpty()) {
            new RuntimeException("栈空");
        }

        int num = head.next.val;
        head.next = head.next.next;
        return num;
    }

    //遍历stack
    public void list() {
        if (isEmpty()) {
            System.out.println("栈空的！");
        } else {
            LinkedList cur = head.next;
            System.out.println("栈顶到栈底：");
            while (cur != null) {
                System.out.println(cur.val);
                cur = cur.next;
            }
        }
    }
}

//节点
class LinkedList {
    public int val;
    public LinkedList next;

    public LinkedList(int val) {
        this.val = val;
    }
}