Java append new column to csv file

Question

I want to calculate some column data and write it to csv file as column. Then after calculating other column of data I want to append it to same file but as new

Answer 1

Something like this perhaps:

public void appendCol(String fileName, ???ArrayList??? data) { //assuming data is of type ArrayList here, you need to be more explicit when posting code

    String lineSep = System.getProperty("line.separator");
    String output = "";
    try{
        BufferedReader br = new BufferedReader(new  FileReader(fileName));
        String line = null;
        int i = 0;
        while ((line = br.readLine()) != null) {
            output += line.replace(
                    lineSep,
                    "," + String.valueOf(data.get(i)) + lineSep);
            i++;
        }
        br.close();
        FileWriter fw = new FileWriter(fileName, false); //false to replace file contents, your code has true for append to file contents
        fw.write(output);
        fw.flush();
        fw.close();
    } catch (Exception e){
        e.printStackTrace();
    } 
}