【面接アルゴリズム問題】O(1)時間複雑度内スタック内最大値を求める

package qiuzhaoprepare;

import java.util.Scanner;
import java.util.Stack;
class MaxValueStack {
	static Stack<Integer> stack = new Stack<Integer>();
	static Stack<Integer> maxStack = new Stack<Integer>();
	
	public void push(int value) {
		if(maxStack.isEmpty() || value>=maxStack.peek())
			maxStack.push(value);
		else
			maxStack.push(maxStack.peek());
		stack.push(value);
	}
	
	public int pop() {
		if(!stack.isEmpty()) {
			int temp = stack.pop();
			maxStack.pop();
			return temp;
		}else
			System.out.print("Error, stack is already empty!");
		return 0;
	}
	
	public int max() {
		return maxStack.peek();
	}
}
public class MaxStack {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] arr = new int[n];
		for(int i=0;i<n;i++)
			arr[i] = sc.nextInt();
		
		MaxValueStack item = new MaxValueStack();
		for(int i=0;i<n;i++)
			item.push(arr[i]);
		int res = item.max();
		
		System.out.print(res);
		sc.close();
	}
}