Performing calculations on column data from file through Java

Question

I am trying to perform certain calculations, such as sum and percentage, from a text file through Java and have it print the results. I was given an original text file that has a few columns of population data. I successfully read that file and wrote an intermediate file containing only the columns needed through one Java program as seen below:

import java.io.*;
import java.util.Scanner;

public class ReadWrite
{
    public static void main(String[] args)
    {       
        try
        {
            BufferedReader in = null;
            in = new BufferedReader(new FileReader("SmallAreaIncomePovertyEstData.txt"));
            PrintWriter out = null;
            out = new PrintWriter(new BufferedWriter(new 
                FileWriter("IntermediateSmallAreaIncomePovertyEstData.txt")));
            String records = null;
            
            while((records = in.readLine()) != null)
            {               
                String stateCode = records.substring(0, 2);
                String districtId = records.substring(4, 8);
                String districtName = records.substring(10, 81);
                String totalPopulation = records.substring(83, 90);
                String schoolAgeChildrenPopulation = records.substring(92, 99);
                String povertyPopulation = records.substring(101, 108);
                String fileName = records.substring(110, 130);
                
                out.printf("%3s%10s%10s%10s\n", stateCode, totalPopulation, 
                 schoolAgeChildrenPopulation, povertyPopulation);
            }
            out.close();
        }
        catch(Exception e)
        {
            System.out.println("Error writing to file.");
        }
    }
}

Where I am stuck is now I must read the intermediate file I created and perform some calculations. This is a snippet of the intermediate file:

01   31754      6475       733   
01   21522      4010      1563   
01   17292      2719      1158   
01    9044      1512       471   
01   22759      3304      1122   
01    8238      1491       250   
01   23494      3767       770   
01    6019       971       283   
01   57441      7120       994   
01   55246     10643      1855   
01  195540     32652      6171   
01   14124      1769       759   
01   27510      4765      2009   
01   22512      3590      1096   
01  212631     30718     12740   
01   51246      9201      2218   
01    9619      1742       464   
01    5354       866       279   
01   10639      1565       684   
01   20265      3494      1430   
01   56502      9945      2162   
01   27696      4343      1348   
01   26203      4163      1184   

There are 56 samples and this snippet just shows a small portion of sample 01. I need to take all the data for sample 01 and add them together. So all the numbers in each of the second, third and fourth columns need to have a sum so that the output for sample 01 would be something like...

01   8368948    747839    87639

And so on. Instead of having pages upon pages of individual data, I would have 56 rows of combined data. I was doing this piece by piece and so far I have the following code:

import java.io.*;
import java.util.Scanner;

public class Test
{
    public static void main(String[] args)
    {       
        try
        {
            BufferedReader in = null;
            in = new BufferedReader(new 
                     FileReader("IntermediateSmallAreaIncomePovertyEstData.txt"));
            String records = null;
            int totalPop = 0;
            String [] population = null;
            
            System.out.println("State Code + Population + Child Population + Child Poverty 
                     Population + % Child Poverty");
            System.out.println("========== + ========== + ================ + 
                     ======================== + ===============");
            
            while((records = in.readLine()) != null)
            {   
                population = records.split("          ");
                totalPop += Integer.parseInt(population[1]);
                
                System.out.println(totalPop);
            }
            in.close();
        }
        catch(Exception e)
        {
            System.out.println("Error writing to file.");
        }
    }
}  

This method is successful until it reaches a number that is smaller or larger than the first. For example, in the data I already showed, I get a successful sum of numbers until I hit 9044 from column 2 since the spacing is different.

01   31754      6475       733   
01   21522      4010      1563   
01   17292      2719      1158   
01    9044      1512       471 

I've tried left justifying my intermediate file so all the numbers would line up but that only helps me with column 2. I would encounter the same issue with columns 3 and 4 since the population data is different in each row.

How do I create a method that would add these values together successfully?

To add on to that, I need to take the last 2 columns of summed data and divide them to create a new column of percent population. I figure once I figure out the addition part, this part will be an easy calculation.

Any advice or wisdom would be appreciated! Thank you!!

Answer 1

Instead of doing split(" ") you could just split with single space, (split(" ")), and then filter blank strings out. List<String> stringList = Arrays.stream(line.split(" ")).filter(word -> !word.isBlank()).collect(Collectors.toList()); As a result you have a List, not an array. But if you need to convert a list to array again, just do String[] strArray = stringList.toArray(new String[0]); For further read, just check this post