Moving average implementation

Algo_MovingAverage.java

public class MovingAverage {

    private final int[] array;
    private int index;
    private long sum;

    public MovingAverage(int size) {
        this.array = new int[size];
        this.index = 0;
    }

    public double next(int value) {
        if (index == array.length) {
            index = 0;
        }
        sum = sum - array[index] + value;
        array[index++] = value;
        return (double) sum / array.length;
    }

    public static void main(String[] args) {
        MovingAverage m = new MovingAverage(3);
        System.out.println(m.next(1));
        System.out.println(m.next(10));
        System.out.println(m.next(3));
        System.out.println(m.next(5));
        System.out.println(m.next(1));
    }
}