public static double variance(Collection<?> inputList, String propertyPath) {
double mean = mean(inputList, propertyPath);
double temp = 0;
double a;
if (propertyPath.contains(".") || propertyPath.contains("[")) {
String[] properties = StringScanner.splitByDelimiters(propertyPath, ".[]");
for (Object o : inputList) {
a = BeanUtils.getPropertyInt(o, properties);
temp += (mean - a) * (mean - a);
}
} else {
Map<String, FieldAccess> fields = BeanUtils.getFieldsFromObject(inputList.iterator().next());
FieldAccess fieldAccess = fields.get(propertyPath);
for (Object o : inputList) {
a = fieldAccess.getInt(o);
temp += (mean - a) * (mean - a);
}
}
return Math.round(temp / inputList.size());
}
/**
* Calculate a sum of a property from a list.
*
* @param inputList
* @param propertyPath to item we want to sum
* @return sum
*/
public static long sum(Collection<?> inputList, String propertyPath) {
if (inputList.size() == 0) {
return 0;
}
long sum = 0l;
if (propertyPath.contains(".") || propertyPath.contains("[")) {
String[] properties = StringScanner.splitByDelimiters(propertyPath, ".[]");
for (Object o : inputList) {
sum += BeanUtils.getPropertyInt(o, properties);
}
} else {
Map<String, FieldAccess> fields = BeanUtils.getFieldsFromObject(inputList.iterator().next());
FieldAccess fieldAccess = fields.get(propertyPath);
for (Object o : inputList) {
sum += fieldAccess.getInt(o);
}
}
return sum;
}
