Question

I tried to Google for an answer but I think I am using wrong keywords. What I am trying to do is – I have a collection of numbers (ints), and as I add new numbers I am computing the new average. I noticed that as my array grows, once I get to a certain count of elements (lets say 200), the calculation time becomes noticeable. I was wondering if there are any built-in SDK functions I can utilize to speed up my codes performance? I will be running the code on Android.

int[] numbers = new int[3];

private int average(int number){
    //some buildin operation to push in array an int?
    for(int i=0; i < numbers.length -1 ; i++){
        numbers[i]=numbers[i+1];
    }
    numbers[numbers.length -1] = number;
                    ;                
    //numbers[0] = numbers[1];
    //numbers[1] = numbers[2];
    //numbers[2] = number;

    int sum = 0;

    //any operation to get average?
    for(int i=0; i < numbers.length ; i++)
        sum = sum + numbers[i];

    //calculate average value
    double average = sum / numbers.length;

    return (int)average;
 }

Answer 1

Now I just made ​​myself a circular buffer (as suggested Oli Charlesworth).

And this is my implementation:

/** Circular buffer */
private class WindowBuffer {
    private final float [] values;
    private final int capacity;
    private float sum;
    private float average;
    private int head = -1;
    private boolean full = false;

    WindowBuffer(final int capacity) {
        this.capacity = capacity;
        values = new float[capacity];
        for (int i = 0; i < capacity; i++) {
            values[i] = 0f;
        }
    }
    void clean() {
        if (head == -1) return;
        for (int i = 0; i < capacity; i++) {
            values[i] = 0f;
        }               
        sum = 0;
        average = 0;
        head = -1;
        full = false;
    }

    void put(final float value) {
        head++;
        if (head >= capacity) {
            head = 0;
            full = true;
        }
        sum -= values[head];
        sum += value;
        values[head] = value;
        calculateAverage();
    }

    private void calculateAverage() {
        if (full) {
            average = sum / capacity;
        } else {
            average = sum / (head + 1);
        }
    }

    float getAverage() {
        return average;
    }
}

UPD

void clean() {
            if (head == -1) return;
            if (full) {
                for (int i = 0; i < capacity; i++) {
                    values[i] = 0f;
                }
            } else {
                for (int i = 0; i <= head; i++) {
                    values[i] = 0f;
                }
            }
            sum = 0;
            average = 0;
            head = -1;
            full = false;
        }