如何将数组元素的总和除以它们的数量？

Question

double array_of_grades[] = new double[number_of_subjects];
double average;

for(int i=0; i < number_of_subjects; i++) {
    array_of_grades[i]=array[i].getGrade();
}

array[] is an array of objects, which contains all the information about each subject. Each subject has 1 grade. I want to get the average grade of all the subjects.

Answer 1

Calculate the sum:

double sum = 0;
for (double grade : array_of_grades) 
    sum += grade;

Then calculate the average:

average = 1.0d * sum / array_of_grades.length;

Answer 2

You can use a stream from directly beginning your process from your array

double avg = Stream.of(array)
                   .mapToDouble(x -> x.getGrade())
                   .average()
                   .getAsDouble();