用两个栈来实现一个队列，完成队列的Push和Pop操作。队列中的元素为int类

 

import java.util.Stack;

 

public class Solution {

    Stack<Integer> stack1 = newStack<Integer>();

    Stack<Integer> stack2 = newStack<Integer>();

     

    public void push(int node) {

        stack1.push(node);

    }

     

    public int pop() {

        if(stack1.empty()&&stack2.empty()){

            thrownew RuntimeException("Queue is empty!");

        }

        if(stack2.empty()){

            while(!stack1.empty()){

                stack2.push(stack1.pop());

            }

        }

        return stack2.pop();

    }

}