JAVA: 包含min函数的栈

题目：定义栈的数据结构，请在该类型中实现一个能够得到栈最小元素的min函数。import java.util.Stack;

public class Solution {

Stack<Integer> data=new Stack<>();
Stack<Integer> mindata=new Stack<>();
Integer temp=null;
public void push(int node) {
if(temp==null){
temp=node;
data.push(node);
mindata.push(node);
}else{
data.push(node);
if(node<=temp){
temp=node;
mindata.push(node);
}
}
}

public void pop() {
int num=data.pop();
int num1=mindata.pop();
if(num!=num1){
mindata.push(num1);
}
}

public int top() {
int num=data.pop();
data.push(num);
return num;
}

public int min() {
int min=mindata.pop();
mindata.push(min);
return min;
}
}