Leetcode: Moving Average from Data Stream

Given a stream of integers and a window size, calculate the moving average of all integers in the sliding window.

For example,
MovingAverage m = new MovingAverage(3);
m.next(1) = 1
m.next(10) = (1 + 10) / 2
m.next(3) = (1 + 10 + 3) / 3
m.next(5) = (10 + 3 + 5) / 3

 1 public class MovingAverage {
 2     Queue<Integer> queue;
 3     int capacity;
 4     int sum;
 5 
 6     /** Initialize your data structure here. */
 7     public MovingAverage(int size) {
 8         queue = new LinkedList<Integer>();
 9         capacity = size;
10         sum = 0;
11     }
12     
13     public double next(int val) {
14         if (queue.size() == capacity) {
15             sum -= queue.poll();
16         }
17         sum += val;
18         queue.offer(val);
19         return (double)sum/queue.size();
20     }
21 }
22 
23 /**
24  * Your MovingAverage object will be instantiated and called as such:
25  * MovingAverage obj = new MovingAverage(size);
26  * double param_1 = obj.next(val);
27  */

 1 public class MovingAverage {
 2     private int [] window;
 3     private int n, insert;
 4     private long sum;
 5     
 6     /** Initialize your data structure here. */
 7     public MovingAverage(int size) {
 8         window = new int[size];
 9         insert = 0;
10         sum = 0;
11     }
12     
13     public double next(int val) {
14         if (n < window.length)  n++;
15         sum -= window[insert];
16         sum += val;
17         window[insert] = val;
18         insert = (insert + 1) % window.length;
19         
20         return (double)sum / n;
21     }
22 }