Java - parse CSV into Arrays based on columns

Question

I would like to ask for help with this task: I have CSV for example like this:

column1$column2$column3
123$xyz$321
456$zyx$654

And I would like to parse it by Java to Arrays / Array lists by columns / headers -> for example

ArrayList column1 = [123,456]
ArrayList column2 = [xyz,zyx]
ArrayList column3 = [321,654]

Thanks everyone.

line.split("$") will give you and array, index 0 ---> list1 (column1) , index 1 --> list 2 column2 ecc. — Petter Friberg
– Petter Friberg, Commented Nov 15, 2015 at 21:06
Welcome to Stack Overflow. Please read stackoverflow.com/help/how-to-ask to help improve your post. — Data Man
– Data Man, Commented Nov 15, 2015 at 21:09

Petter Friberg · Accepted Answer · 2015-11-15 22:04:41Z

2

This is how I would have done this..., note the metod to put the columns in another List for less code and to be more dynamic.

public static void main(String[] args) {
    ArrayList<ArrayList<String>> columns = new ArrayList<ArrayList<String>>();
    BufferedReader br = null;
    try {
        String sCurrentLine;
        br = new BufferedReader(new FileReader("testing.cvs"));

        while ((sCurrentLine = br.readLine()) != null) {
            String[] fields = sCurrentLine.split("\\$");
            for (int i = 0; i < fields.length; i++) {
                if (columns.size()<=i){
                    columns.add(new ArrayList<String>());
                }
                columns.get(i).add(fields[i]);
            }
        }

    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            if (br != null)br.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

edited Nov 15, 2015 at 22:04

answered Nov 15, 2015 at 21:55

Petter Friberg

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4 Comments

Pavel Straka Over a year ago

Thanks, it works well. But could You please be so gentle and extend Your solution by automatic-counter of columns? So I did not have to manually enter the value of columns?

Pavel Straka Over a year ago

I am sorry, maybe I wrote my question wrong. Now I am not sure, if this is what I needed. I need to access to every column by String index (the header of column). Should I use HashMaps instead of ArrayLists?

Petter Friberg Over a year ago

Thats surely one method to do it... but I guess you need to open a new question, if you have still problem... you should use a HashMap that contains ArrayList...

Pavel Straka Over a year ago

OK, I will open another question, Thank you.

Abdelhak · Accepted Answer · 2015-11-15 21:39:10Z

I thin this can help you to fix the problem just tery it.

public static void main(String[] args) {
    Scanner s = null;
    try {
        s = new Scanner(new File("C:\\temp\\file.txt"));
        ArrayList lis1 = new ArrayList();
        ArrayList lis2 = new ArrayList();
        ArrayList lis3 = new ArrayList();

        while (s.hasNext()) {

            String d = s.nextLine();
            lis1.add(d.split("\\$")[0]);
            lis2.add(d.split("\\$")[1]);
            lis3.add(d.split("\\$")[2]);

        }

        for (Object l : lis1) {
            System.out.print(l+" ");
        }
        System.out.print("\n ");
        for (Object l : lis2) {
            System.out.print(l+" ");
        }
        System.out.print("\n ");
        for (Object l : lis3) {
            System.out.print(l+" ");
        }

    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
}

you can use the result when you wont

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