Java Utililty Methods Collection Average

double sum = 0;
for (Object x : a) {
    if (x instanceof Double) {
        sum += (Double) x;
    } else if (x instanceof Long) {
        sum += (Long) x;
    } else if (x instanceof Integer) {
        sum += (Integer) x;
...

return sum(col) / col.size();

double sum = 0.0;
int count = sizes.size();
for (double size : sizes) {
    sum += size;
return count > 0 ? sum / count : 0.0;

List<Double> filteredValues = filterNulls(values);
if (filteredValues.size() == 0)
    return null;
double sum = 0;
for (Double value : filteredValues) {
    sum += value;
return sum / filteredValues.size();
...

long avg = 0;
for (Long value : values) {
    avg += value;
return avg / values.size();

double average = 0;
for (T value : values)
    average += value.doubleValue();
average /= values.size();
return average;

double sum = 0;
for (Number value : values) {
    sum += value.doubleValue();
return sum / values.size();