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。在该栈中，调用min、push及pop的时间复杂度都是O(1)。
import java.util.Stack;
public class Solution {
Stack<Integer> dataStack = new Stack<Integer>();
Stack<Integer> minStack = new Stack<Integer>();
public void push(int node) {
Integer temp = new Integer(node);
dataStack.push(temp);
if (minStack.empty()) {
minStack.push(temp);
} else {
int min = minStack.peek().intValue();
if (node > min) {
minStack.push(minStack.peek());
} else {
minStack.push(temp);
}
}
}
public void pop() {
dataStack.pop();
minStack.pop();
}
public int top() {
return dataStack.peek();
}
public int min() {
return minStack.peek();
}
}