Sums

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;

public class Main
{
    public static void main(String[] args) throws IOException
    {
        FileReader file;
        BufferedReader reader;
        String line;
        ArrayList<Integer> numbers = new ArrayList<>();

        //files with data
        String[] fileNames = new String[] {"dane5-1.txt", "dane5-2.txt", "dane5-3.txt"};
        for (String name : fileNames)
        {
            //load single file
            file = new FileReader("/path/to/file/" + name);
            reader = new BufferedReader(file);

            line = reader.readLine();
            while (line != null)
            {
                //append all numbers in file to an ArrayList
                numbers.add(Integer.parseInt(line.trim()));
                line = reader.readLine();
            }

            System.out.println("Największa suma w pliku " + name + " jest równa " + getBestSum(numbers)); //call a function with ArrayList as parameter
            numbers.clear();
        }
    }

    public static int getBestSum(ArrayList<Integer> numbers)
    {
        ArrayList<Integer> sums = new ArrayList<>(); //storage for all sums
        int sum = 0;

        for (int i = 0; i < numbers.size(); i++) //left index
        {
            for (int j = numbers.size() - 1; j >= i; j--)  //right index
            {
                for (int k = j; k >= i; k--)  //addition numbers in a range from right index to left index
                {
                    sum += numbers.get(k);
//                    System.out.print((numbers.get(k)) > 0 ? "+" + numbers.get(k) : numbers.get(k));
                }
//                System.out.print("=" + sum+ '\n');
                sums.add(sum); //append sum to an array
                sum = 0; //reset sum variable
            }
        }

        return Collections.max(sums);
    }
}