How to print two ArrayLists to a csv file with multiple columns?

Question

I have two array lists like shown below,

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.*;

class Reader {
    public static void main(String args[]) throws FileNotFoundException {

        ArrayList<String> animal = new ArrayList<>();
        animal.add("Dog");
        animal.add("Cat");
        animal.add("Mouse");

        ArrayList<Integer> numbers = new ArrayList<>();
        for (int i = 1; i <= 15; i++) {
            numbers.add(i);
        }

        PrintWriter writer = new PrintWriter("animals.csv");

        for (String ani : animal) {
            writer.println(ani + ",");
        }

        writer.close();    
    }
}

I want the output to be like this in the .csv file.

Dog,1,2,3,4,5,
Cat,6,7,8,9,10,
Mouse,11,12,13,14,15,

When I use for-loops, the output of the array lists gets printed one below the other in the .csv file.

How do I format the array lists the way I desired, so it looks like this in Excel?

writer.println(ani + ","); remove ln and use writer.print(ani + ","); — bananas
– bananas, Commented Nov 11, 2016 at 3:47
@KematRochi: what is the condition for number? Is it fixed 5 numbers for each animal? — Tanmay Baid
– Tanmay Baid, Commented Nov 11, 2016 at 3:54

Tanmay Baid · Accepted Answer · 2016-11-11 04:09:59Z

1

use writer.print() instead of writer.println()

Notice 'ln' in the method name you are using, which means print line.

Update: To also add numbers along with animal:

public static void main(final String[] args) throws FileNotFoundException {
    ArrayList<String> animal = new ArrayList<>();
    animal.add("Dog");
    animal.add("Cat");
    animal.add("Mouse");

    ArrayList<Integer> numbers = new ArrayList<>();
    for (int i = 1; i <= 15; i++) {
        numbers.add(i);
    }

    PrintWriter writer = new PrintWriter("animals.csv");

    List<String> row = new ArrayList<>();
    int i = 0;
    for (String ani : animal) {
        row.add(ani);
        for (int j = 0; j < 5; j++) {
            row.add(String.valueOf(numbers.get(i++)));
        }
        writer.println(String.join(",", row));
        row.clear();
    }

    writer.close();
}

edited Nov 11, 2016 at 4:09

answered Nov 11, 2016 at 3:47

Tanmay Baid

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2 Comments

bananas Over a year ago

stringjoiner is available in java8 too

Kemat Rochi Over a year ago

I tried this code and seems to be working great to meet my requirements.

bhavya.work · Accepted Answer · 2016-11-11 04:31:57Z

0

Your writer method is printing a line. You need to use just print.

So writer.println(ani + ","); becomes writer.print(ani + ",");

Also, to add numbers as you asked you can do this as an alternative. This works as you said you have only 5 elements in each row after animal name.

PrintWriter writer = new PrintWriter("animals.csv");
int rowCounter = 0;
for (String ani : animals) {
  writer.print(ani);
  for (int i = rowCounter * 5; i < (rowCounter * 5 + 5); i++) {
    writer.print("," + numbers.get(i));
  }
  writer.println();
  rowCounter++;
}

writer.close();

edited Nov 11, 2016 at 4:31

answered Nov 11, 2016 at 3:48

bhavya.work

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