顺序表代码

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
    public int top;
    public Object[] objArray;
    
    //初始化
    public Ideone(int defaultSize)
    {
        objArray = new Object[defaultSize];
        top = -1;
    }
    
    //判断是否为空
    public boolean isEmpty()
    {
        boolean flag = false;
        if(top == -1)
        {
            flag = true;
        }
        return flag;
    }
    
    //获取栈顶元素
    public Object getTop()
    {
        if(!isEmpty())
        {
            return objArray[top];
        }
        System.out.println("栈为空");
        return null;
    }
    //栈顶插入数据
    public void push(Object obj)
    {
        if(top + 1 >= objArray.length)
        {
            System.out.println("栈已满,无法添加"+obj);
            return ;
        }
        objArray[top+1] = obj;
        top++;
    }
    
    //栈顶弹出数据
    public Object pop()
    {
        if(isEmpty())
        {
            System.out.println("栈已空");
            return null;
        }
        Object obj = objArray[top];
        objArray[top--] ="";
        return obj;
    }
    
    public static void main (String[] args) throws java.lang.Exception
    {
        // your code goes here
        Ideone s = new Ideone(2);
        s.push("a");
        s.push("b");
        s.push("c");
        System.out.println(s.getTop());
        System.out.println(s.pop());
        System.out.println(s.getTop());
        s.pop();
        System.out.println(s.getTop());
    }
}