用俩个栈实现队列

 1 import java.util.Stack;
 2 public class Solution {
 3     Stack<Integer> stack1 = new Stack<Integer>();
 4     Stack<Integer> stack2 = new Stack<Integer>();
 5      
 6     public void push(int node) {
 7         stack1.push(node);
 8     }
 9      
10     public int pop() {
11         if(stack1.empty()&&stack2.empty()){
12            System.out.println("The queue is empty!");
13         }
14         if(stack2.empty()){ 
15             while(!stack1.empty()){
16                 stack2.push(stack1.pop());
17             }
18     }
19         return stack2.pop();
20     }
21 }