学习笔记-用单链表写栈的过程

上一篇文章是用数组写的，这篇用的单链表写的。

public class LinkedListStack {
    public static void main(String[] args) {
        LinkedStack as = new LinkedStack();
        String key = "";
        boolean flag = true;
        Scanner sc = new Scanner(System.in);
        while (flag){
            System.out.println("show: 显示数据");
            System.out.println("exit: 退出");
            System.out.println("push: 添加");
            System.out.println("del: 取出");
            System.out.println("请输入你的选择");
            key = sc.next();
            switch (key){
                case "show":
                    as.show();
                    break;
                case "exit":
                    flag = false;
                    break;
                case "del":
                    try {
                        as.pop();
                    }catch (Exception e){
                        System.out.println(e.getMessage());
                    }
                    break;
                case "push":
                    System.out.println("请输入你要添加的数据");
                    int value = Integer.parseInt(sc.next());
                    Linked bb = new Linked(value);
                    as.push(bb);
                    break;
                default:
                    break;
            }
        }

    }
}
class LinkedStack{
    private Linked l = new Linked(0);
    public void push(Linked linked){
        Linked temp = l;
        if (temp.next == null){
            temp.next = linked;
        }else {
            linked.next = temp.next;
            temp.next = linked;
        }
    }
    public void pop(){
        Linked temp = l;
        if (temp.next == null){
            throw new RuntimeException("无数据，无法取出");
        }
        Linked value = temp.next;
        temp.next = temp.next.next;
        System.out.printf("出栈的是%d\n", value.num);
    }
    public void show(){
        Linked temp = l;
        if (temp.next == null){
            System.out.println("空");
            return;
        }
        while (true){
            if (temp.next == null){
                break;
            }
            System.out.printf("栈里的数据为%d\n", temp.next.num);
            temp = temp.next;
        }
    }
}

class Linked{
    public int num;
    public Linked next;
    //构造器
    public Linked(int num) {
        this.num = num;
    }

    @Override
    public String toString() {
        return "Linked{" +
                "num=" + num +
                ", next=" + next +
                '}';
    }
}