How do you loop through a column of a csv file to find a certain string in java?

Question

I want to be able to loop through the second column of a csv file and find the indexes of a particular string. So for example find all the indexes with the value "Chelsea". Below is the code I have so far.

Any Help?

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class CSVReader {

    public static void main(String[] args) {
        CSVReader obj = new CSVReader();
        obj.run();
    }

    public void run() {
        String csv = "2015:2016.csv";
        BufferedReader br = null;
        String line = "";
        String csvSplit = ",";
        String[] football = new String[0];
        try {
            br = new BufferedReader(new FileReader(csv));
            String headerLine = br.readLine();

            while ((line = br.readLine()) != null) {
                football = line.split(csvSplit);
            }
        }
        catch (IOException io) {
            System.out.println(io);
        }
    }
}

football[1] will give you second column. Also, you will probably need a loop or an even better approach (like reading all the lines at once using the Files.readAllLines() — TheLostMind
– TheLostMind, Commented May 31, 2016 at 18:09
Files.readAllLines()will load all your file into memory so make sure that the file will never be big before using this appraoch — Nicolas Filotto
– Nicolas Filotto, Commented May 31, 2016 at 18:12

Brandon McKenzie · Accepted Answer · 2016-05-31 18:29:35Z

2

In terms of finding Chelsea, you are only an if statement away at minimum. Merge this code into your while loop:

while ((line = br.readLine()) != null) {
    football = line.split(csvSplit);
    if(football[1].equals("Chelsea") {
        System.out.println("I found Chelsea!");
    }
}

Of course, I imagine you'll want to be a little informative than that. If you wanted to provide a line number for the line Chelsea was on, you could do something like:

int index = 1;
while ((line = br.readLine()) != null) {
    football = line.split(csvSplit);
    if(football[1].equals("Chelsea") {
        System.out.println("I found Chelsea on line " + index);
    }
    index++;
}

Alternatively, if you want to work with one or all elements of Chelsea's row, you could do something like:

while ((line = br.readLine()) != null) {
    football = line.split(csvSplit);
    if(football[1].equals("Chelsea") {
        System.out.println("I found Chelsea on row with first column equal to " + football[0]);
        System.out.println("The entire row consists of: ");
        for(int i = 0; i < football.length; i++) {
            System.out.print(football[i] + ", ");
        }
        System.out.println();
    }
}

Or you can feed Chelsea's line to another part of your program to do other fancy things with it.

answered May 31, 2016 at 18:29

Brandon McKenzie

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1 Comment

matebannan Over a year ago

Great just what I needed! Thank you!

MAZDAK · Accepted Answer · 2016-05-31 18:20:34Z

1

Here is a solution that is a bit different from your solution but does what you want.

public class Main {

public static void main(String[] args) throws FileNotFoundException, IOException {

    BufferedReader bfr = new BufferedReader(new FileReader("path_2_csv_file"));

    List<Integer> results = new ArrayList<>();
    String  l= "";
    int index = 1;
    while((l = bfr.readLine()) != null){

        //break each line of the csv file to its elements
        String[] elements=l.split(",");

        //check if the second column is equal to e.g. Chelsea
        if(elements[1].equals("Chelsea")){
            results.add(index);
        }

        index++;
    }

    //print the results
    for(Integer i : results){
        System.out.println(i);
    }
  }
}

answered May 31, 2016 at 18:20

MAZDAK

5831 gold badge4 silver badges17 bronze badges

3 Comments

matebannan Over a year ago

Hi Meghi, okay great thanks, once I find the indexes, is there anyway to use these indexes to find the corresponding value in the next column?

MAZDAK Over a year ago

Yes. Create a List<String[]> allLines = new ArrayList<String[]>(). At each iteration of the while loop store the line in this List. allLines.add(l.split(",")).

MAZDAK Over a year ago

Then you can access the desired index (line) by allLines.get(i-1).

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