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

public class MovingAverage {

    private int size;
    private double sum;
    private ArrayDeque<Integer> queue;
    public MovingAverage(int size) {
        this.size = size;
        this.sum = 0;
        this.queue = new ArrayDeque<Integer>();
    }

    public double next(int val) {
        if (queue.size() == size) {
            sum -= queue.remove();
        }
        queue.offer(val);
        sum += val;
        return sum / queue.size();
    }
}

https://discuss.leetcode.com/topic/50122/100-java-solution-with-deque

deque：https://docs.oracle.com/javase/7/docs/api/java/util/ArrayDeque.html