链栈

不念不忘少年蓝@ 2022-07-19 02:17 129阅读 0赞

package com.loong.datastructure;
    
    /** * 链栈 * * @author Loong * @param <E> * */
    public class LinkedStack { 
        Node first;
    
        /** * 获取栈顶元素 * * @return */
        public Object getTop() {
            if (isStackEmpty()) {
                throw new RuntimeException("栈为空");
            } else {
                return first;
            }
        }
    
        /** * 压栈 * * @param o */
        public void add(Object o) {
            Node n = new Node(o, first);
            first = n;
        }
    
        /** * 退栈 * * @return */
        public Object pop() {
            if (isStackEmpty()) {
                throw new RuntimeException("栈为空");
            } else {
                first = first.next;
                return first;
            }
        }
    
        /** * 判断栈是否为空 * * @return */
        public boolean isStackEmpty() {
            return first == null;
        }
    
        private static class Node { 
            Object item;
            Node next;
    
            Node(Object element, Node next) {
                this.item = element;
                this.next = next;
            }
        }
    
        public static void main(String[] args) {
            LinkedStack ls = new LinkedStack();
    
            ls.add("zhong");
            ls.add("2");
            ls.add("3");
            ls.add("4");
            Node n = (Node) ls.getTop();
            System.out.println(n.item);
            ls.pop();
            n = (Node) ls.getTop();
            System.out.println(n.item);
            ls.pop();
            n = (Node) ls.getTop();
            System.out.println(n.item);
            ls.pop();
            n = (Node) ls.getTop();
            System.out.println(n.item);
            ls.pop();
            n = (Node) ls.getTop();
            System.out.println(n.item);
        }
    }