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() {
        while(!stack1.isEmpty())
            stack2.push(stack1.pop());
        int res = stack2.pop();
        while (!stack2.isEmpty())
            stack1.push(stack2.pop());
        return res;     
    }
}