ArrayList Integer - calculate average grade without considering extreme values

Question

How to calculate average grades (arithmetic method) in such a way that the extreme grades (6) will be removed from list - and the smallest (1) will be removed from list?

import java.util.*;
import java.lang.*;
import java.io.*;

class ListOfGrades
{
    public static void main (String[] args) throws java.lang.Exception
    {
        //Create and fill the list 
        ArrayList<Integer> grades = new ArrayList<Integer>();
        grades.add(1);
        grades.add(2);
        grades.add(3);
        grades.add(4);
        grades.add(5);
        grades.add(6);

        for(int i=0; i < grades.size(); i++) {
            System.out.println("Element : [" + i + "] grades " +  grades.get(i)) ;  
        }
        System.out.println();
        System.out.println("Removing last Element");
        grades.remove(grades.size()-1);
        System.out.println("Now all grades are : " + grades);
        System.out.println();
        System.out.println("Removing first Element");
        grades.remove(grades.size()-5);
        System.out.println("Now all grades are : " + grades);
    }
}

youre code is already removing the extreme values, what do you want it to do? — abdulwasey20, Feb 16 '19 at 16:30
Possible duplicate of [How to efficiently compute average on the fly (moving average)?](https://stackoverflow.com/questions/28820904/how-to-efficiently-compute-average-on-the-fly-moving-average) — EJoshuaS - Stand with Ukraine, Feb 16 '19 at 16:32
The solution is the same as the linked question, except that you ignore 6 and 1. — EJoshuaS - Stand with Ukraine, Feb 16 '19 at 16:33
You should use grades.remove(grades.size()-(grades.size()-1)); so it is more generic. — abdulwasey20, Feb 16 '19 at 16:40

abdulwasey20 · Accepted Answer · 2019-02-16T16:41:50.153

1

You can add this simple code at the end of your previously written code:

int sum=0;
for (int i=0; i<grades.size();i++){
    sum+=grades.get(i);               //adding all the grades in variable sum
}
double avg= sum/grades.size();      //dividing the sum with total number of 
                                    //grades to calculate average
System.out.println("average grade :" + avg);

edited Feb 16 '19 at 16:41

answered Feb 16 '19 at 16:36

abdulwasey20

747
8
21

1

only one thing in the first line it should be "double" – Martin Feb 16 '19 at 16:54
that will only be required when your ArrayList is of type and you add decimal numbers in the array. Since you are adding whole numbers in the array only, their sum will also be a whole number always. So no need of "double" sum in this case. – abdulwasey20 Feb 16 '19 at 16:58

score 1 · Answer 2 · answered Feb 16 '19 at 16:55

1

There is solution with stream api using Collectors::averagingDouble:

Double average = grades.stream()
            .collect(Collectors.averagingDouble(value -> value));

answered Feb 16 '19 at 16:55

Ruslan

6,090
1
21
36

score 1 · Answer 3 · answered Feb 16 '19 at 17:07

1

I tried something like this :

 grades.stream().filter(g -> !(g == 1 || g == 6))
                   .reduce((grade, sum) -> grade + sum)
                   .map(sum -> sum / 4)
                   .orElse(0);

answered Feb 16 '19 at 17:07

Thida Tun

48
4

ArrayList Integer - calculate average grade without considering extreme values

3 Answers3