剑指offer5：用两个栈实现队列

 1 import java.util.Stack;
 2 public class Lianggezhanduilie {
 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         while(stack2.isEmpty()){
12             while(!stack1.isEmpty()){
13                 stack2.push(stack1.pop());    
14             }
15         }
16         int ans = stack2.pop();
17     return ans;
18        
19     }
20     public static void main(String[] args) {
21         // TODO Auto-generated method stub
22 
23     }
24 
25 }