How to replace empty cell of a CSV with text as NULL using Java

Question

I have input CSV. One of the columns has no value in the cell. While writing the data to another CSV I want to write NULL in that empty cell. I tried to replace "" with NULL but then it prints NULL in all cells. Also, I want to exclude adding NULL text in hard-coded columns of the code i.e. UniqueId, IsDelete, Rootpid. I want them to be empty.

Here is my code so far:

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


        String sourceFilePath = "C://MyData/Emp_Input.csv";
        String newFilePath = "C://MyData/Emp_Output.csv";
        File sourceCsvFile = new File(sourceFilePath);
        File finalCsvFile = new File(newFilePath);
        final Charset Encoding = Charset.forName("UTF-8"); 
        String cvsSplitBy = ",";


        String line = "";

        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(finalCsvFile), Encoding));


        try (BufferedReader br = new BufferedReader(new FileReader(sourceCsvFile))) 
        {
            line = br.readLine(); 
            String newFileLine = "UniqueID" + cvsSplitBy +line + cvsSplitBy  + "IsDelete" + cvsSplitBy + "Rootpid";
            writer.write(newFileLine);   
            writer.newLine();


            while ((line = br.readLine()) != null)  
            {   
            /*  if (line.contains("") )
                {

                    line = line.replace("", "NULL"); // missing code to replace empty cell of a csv with text as NULL
                } */


                else if (line.contains("TRUE") || line.contains("FALSE"))
                {
                    line = line.replace("TRUE", "1");
                    line = line.replace("FALSE", "0");

                } 


                    newFileLine =  cvsSplitBy + line + cvsSplitBy + cvsSplitBy;
                    writer.write(newFileLine);  
                    writer.newLine();


            }

            writer.close();

        }


    }

Lho Ben · Accepted Answer · 2018-12-08 19:18:55Z

1

It is impossible, there is no difference between empty and null strings in csv.

answered Dec 8, 2018 at 19:18

Lho Ben

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3 Comments

Vikas J Over a year ago

Agreed! But I have a requirement for further process of the application I want NULL as a text to be written in those cells which are empty.

Lho Ben Over a year ago

You can configure excel to show NULL for empty strings in your csv, but if you write null in cvs, it's the value "null" which is of course different from empty and null object

Vikas J Over a year ago

Yes I want value null to be written in CSV.

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