public class Client {
    public static void main(String[] args) {
        Student[] students = {
                new Student(100),
                new Student(98),
                new Student(72),
        };

        double average = average(students);

        System.out.println(average); // 90.0
    }

    public static double average(Measurable[] objects) {
        double sum = 0;
        for (Measurable object : objects) {
            sum += object.getValue();
        }
        int length = objects.length;
        return sum / length;
    }
}


public class Student implements GetInfo {
    private double score;

    public Student(double score) {
        this.score = score;
    }

    @Override
    public double getValue() {
        return this.score;
    }
}


public interface Measurable {
    double getValue();
}


public interface GetInfo extends Measurable{
}