题解 | #用两个栈实现队列#

import java.util.Stack;

public class Solution {
    Stack<Integer> stack1 = new Stack<Integer>();
    Stack<Integer> stack2 = new Stack<Integer>();

    public void push(int node) {
        stack1.push(node);
    }

    public int pop() {
	  // 不为空再从stack1获取数据，为了防止stack没有全部弹完，导致又push新元素导致顺序乱
        if (stack2.isEmpty()) {
            while (stack1.size() > 0) {
                stack2.push(stack1.pop());
            }  
        }
        
        return stack2.pop();
    }

}