A tiny OOP challenge (Python, Java, C++, any language with class) /

Let's try something different. A task.

Write a class "Averager" which must be able to compute the average of a whole bunch of numbers. Here are the methods to be implemented:

void add(double number) ... add a number to the dataset
double getAverage() ... gives the average of all numbers
double getSum() ... gives the sum of all numbers
int getNum() ... gives the count of all numbers so far
void reset() ... empty data set

Here's an example call and use of this calls in C++:

int main()
{
    double testvals[] = { 3.0, 2.0, 1.0, 0.0, 4.0 };
    Averager *averager = new Arerager();
    int num = sizeof(testvals) / sizeof(double);
    for (int i = 0; i < num; i++)
    {
        averager->add(testvals[i]);
    }
    cout << "Durchschnitt: " << averager->getAverage() << endl; // 2.0
    cout << "Summe:        " << averager->getSum() << endl; // 10.0
    cout << "Anzahl:       " << averager->getNum() << endl; // 5

    averager.reset();

    for (int i = 0; i < num; i++)
    {
        averager->add(testvals[i]);
        averager->add(testvals[i]);
    }
    cout << "Durchschnitt: " << averager->getAverage() << endl; // 2.0
    cout << "Summe:        " << averager->getSum() << endl; // 20.0
    cout << "Anzahl:       " << averager->getNum() << endl; // 10
}