346. Moving Average from Data Stream

class MovingAverage {

    /** Initialize your data structure here. */
    int[] ary = new int[0];
    int cursize = 0, sum = 0, pos = 0;
    public MovingAverage(int size) {
        ary = new int[size];
    }

    public double next(int val) {
        if(cursize < ary.length) cursize++;
        sum -= ary[pos];
        sum += val;
        ary[pos] = val;
        pos = (pos + 1) % ary.length;
        return (double) sum / cursize;
    }
}

/**
 * Your MovingAverage object will be instantiated and called as such:
 * MovingAverage obj = new MovingAverage(size);
 * double param_1 = obj.next(val);
 */