Writing/Altering csv file java

Question

I am loading a CSV file and kept alive without closing BufferReader. Now I want to add/delete few more rows to my CSV and get updated CSV. Which means I want dynamically notified when CSV file is altered.

Here is my sample code:

public class Check {


    public static void main(String args[]) throws IOException, InterruptedException{
        Check ch = new Check();
        //args[0] = "C:\\Users\\raponnam\\Desktop\\GxDefault.csv";
        String csvFile="C:\\Users\\raponnam\\Desktop\\GxDefault.csv";

        int lineCounter=0;
        if (csvFile!=null)
        {
            BufferedReader csvToRead = null;
            try{
                csvToRead = new BufferedReader(new FileReader(csvFile));
                String line;
                while ((line=csvToRead.readLine())!=null)
                {
                    lineCounter++;
                    String[] splitLine = line.split(",");
                    System.out.println("no of lines-->> "+lineCounter);
                }
                while(true)
                {

                    System.out.println("wait 6 seconds");
                    Thread.sleep(6000);
                }
            }finally{
                //csvToRead.close();
            }
        }
    }
}

take a look if its meaningful : http://stackoverflow.com/a/15128402/1283215 — Hussain Akhtar Wahid 'Ghouri', Nov 06 '13 at 09:47
Use WatchService of Java and filter out for a specific events. http://docs.oracle.com/javase/tutorial/essential/io/notification.html http://stackoverflow.com/questions/16251273/can-i-watch-for-single-file-change-with-watchservice-not-the-whole-directory — Abhijith Nagarajan, Nov 06 '13 at 09:52
You could also use Apache Commons IO library http://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/monitor/package-summary.html — Abhijith Nagarajan, Nov 06 '13 at 10:04

score 1 · Answer 1 · answered Nov 06 '13 at 10:15

CSV handling is far more complicated than you would first think.

The issues causing the nightmares are the different column separators, locales (e.g., if you use , for column separators it might fire back with doubles on some locales, since it is used to denote the decimals), columns are sometimes wrapped with special characters (like " or '), escaping comes into the picture, etc.

If you allow me to have an advice, use a mature CSV lib for the task like OpenCSV (but there are tons of alternatives there). It's quite trivial to use, see the linked site for examples.

score 0 · Answer 2 · answered Nov 06 '13 at 10:04

Use this. Have restructured your code. If readLine returns a number after returning nulls, you can assume that something has been added to the csv file.

PS: If file contents are deleted; the code doesnt work.

String csvFile = "C:\\a.csv";

    int lineCounter = 0;
    if (csvFile != null) {
        BufferedReader csvToRead = null;
        try {
            csvToRead = new BufferedReader(new FileReader(csvFile));
            String line;
            while (true) {
                if ((line = csvToRead.readLine()) != null) {
                    lineCounter++;
                    String[] splitLine = line.split(",");
                    System.out.println("no of lines-->> " + lineCounter);
                }
                System.out.println("wait 6 seconds");
                Thread.sleep(6000);
            }
        } finally {
            // csvToRead.close();
        }
    }

Writing/Altering csv file java

2 Answers2

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