题解 | #用两个栈实现队列#

import java.util.*;
import java.util.Stack;

public class Solution {
    Stack<Integer> stack1 = new Stack<Integer>();
    Stack<Integer> stack2 = new Stack<Integer>();
    //栈1存元素
    public void push(int node) {
        stack1.push(node);
    }
    //取元素先从栈1一次pop出元素push到栈2，取栈2顶端元素出栈，最后栈2元素反向存储到栈1
    public int pop() {
        while(!stack1.isEmpty()){
            stack2.push(stack1.pop());
        }
        int ret = stack2.pop();
        while(!stack2.isEmpty()){
            stack1.push(stack2.pop());
        }
        return ret;
    }
}