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public class Stack {

    //栈的大小
    private int maxstack;
    //用数组来模拟栈
    private int[] stack;
    //表示栈顶所在位置，默认情况下如果没有数据时，使用-1；
    private int top=-1;

    public Stack(int maxstack){
        this.maxstack=maxstack;
        stack=new int[maxstack];
    }
    /**
     * 1.进栈
     * 2.出栈
     * 3.判断是否是空栈
     * 4.当前栈中是否是满栈
     */

    //当前栈中是否是满栈
    public boolean isFull(){
        return  this.top==this.maxstack-1;
    }
    //判断是否是空栈
    public boolean isEmpty(){
        return this.top==-1;
    }
    //进栈
    public void push(int val){
        //是否已经栈满
        if (isFull()){
            throw new RuntimeException("栈满");
        }
        top++;
        stack[top]=val;
    }
    //出栈
    public int pop(){
        if (isFull()){
            throw new RuntimeException("空栈");
        }
        int value=stack[top];
        top--;
        return value;

    }
    //查看栈中所有元素
    public void list(){
        if (isFull()){
            throw new RuntimeException("空栈");
        }
        for (int i = 0; i < stack.length; i++) {
            System.out.printf("stack[%d]=%dn",i,stack[i]);
        }
    }
    //栈中元素存在个数
    public int length(){
        return this.top+1;
    }
}

public class Main {
    public static void main(String[] args) {
        //回文
        System.out.println(huiwen("hello"));
        System.out.println(huiwen("aba"));
    }
    public static boolean huiwen(String val){
        //初始化栈对象
        Stack s=new Stack(10);
        //获取字符串长度
        int length=val.length();
        //把字符串数据逐次获取字符压栈至数组中
        for (int i = 0; i < length; i++) {
            s.push(val.charAt(i));
        }
        //获取
        String newval="";
        int length1=s.length();
        for (int i = 0; i < length1; i++){
            //是否是空栈
            if (!s.isEmpty()){
                char pop=(char)s.pop();
                newval=newval+pop;
            }
        }
        if (val.equals(newval)){
            return true;
        }
        return false;
    }
}