java用链表写栈

如果栈用尾插法，那么先进后出的问题不好解决。所以采用头插法

package link;

import java.util.HashMap;
import java.util.Map;

public class LinkStack {
    int size = 0;
    LinkNode front;//队头指针，指向队头节点
    public boolean isEmpty() {
        return size == 0 ? true : false;
    }

    public boolean push(int x){
        LinkNode linkNode = new LinkNode(x);
        if(front == null){
            front = linkNode;
            size++;
            return true;
        }
        Map<String,String> s = new HashMap<>();
        linkNode.next = front;
        front = linkNode;
        size++;
        return true;
    }

    public boolean pop(){
        if(isEmpty()){
            System.out.println("当前栈为空");
            return false;
        }
        front = front.next;
        size--;
        return true;

    }

    @Override
    public String toString() {
        return front.toString();
    }

    public static void main(String[] args) {
        LinkStack linkStack = new LinkStack();
        linkStack.push(1);
        linkStack.push(2);
        linkStack.push(3);
        System.out.println(linkStack);
        linkStack.pop();
        System.out.println(linkStack);
    }
}