Parse CSV file in java, and delaing with empty values

Question

I am parsing a CSV file into my program, spliting the values at the , element, and it's working fine, except for when I have lines that have missing values.

The parser is working like this:

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class CsvReader
{
    private static final String DELIMITER = ",";
    private final BufferedReader br;
    private final String path;

    public CsvReader(final String path) throws IOException
    {
        this.path = path;
        this.br = new BufferedReader(new FileReader(path));
    }

    public String[] nextLine() throws IOException
    {
        final String line = br.readLine();
        return (line == null) ? new String[0] : line.split(DELIMITER);
    }
}

The lines of data look like this (one line as an example):

J1024205,5028197000004,1,,00,20150603,,Accessories,Factory Test Article (m),ENG,010,110,5,T1,99,99,,,99,99,99,ZZ,ZZ,,5028197242053,30,35028197242054,6,,,OPZ848,3013607800239,OPZ848,,,,50,,

Most of the lines in the file complete with this: 50,85028197242127,8640

But on some lines, the data is missing, so it ends like this: 50,,

When the file is being processed, these lines are causing a java.lang.ArrayIndexOutOfBoundsException.

How can I best deal with this, if I know that the numbers of objects in the file will remain constant?

I've been told that I need to replace empty values with a null value.

before doing split, use line.replace for '' to 'null'. since u need to replace the empty values with null. — Jishnu Prathap
– Jishnu Prathap, Commented Aug 18, 2015 at 9:15

Codebender · Accepted Answer · 2015-08-18 09:14:08Z

15

From the Javadoc of String.split(regex)

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

So, in your case, when the string ends with ,,, empty strings wont be part of the resultant array.

To Fix: Use this variant of split

line.split(DELIMITER, -1);

This will include all trailing empty strings. So you won't get an exception.

answered Aug 18, 2015 at 9:14

Codebender

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4 Comments

Willi Mentzel Over a year ago

This is the best answer for this problem because an empty field should yield an empty String :)

Jishnu Prathap Over a year ago

@haywire No OP needs a null for empty values.

Willi Mentzel Over a year ago

so, he uses the code of Codebender and replaces every "" by null. problem solved.

Willi Mentzel Over a year ago

i have written it down in an answer in case it helps.

Willi Mentzel · Accepted Answer · 2015-08-18 11:14:39Z

1

This code results in array elements that are null if the column was empty.

// ... rest of OP's code

public String[] nextLine() throws IOException
{
    final String line = br.readLine();

    if(line == null)
    {
        return null; 
    }

    String columns[] = line.split(DELIMITER, -1);

    for(int i = 0; i < columns.length; i++)
    {
        if(columns[i].isEmpty())
        {
            columns[i] = null;
        }
    }

    return columns;
}

edited Aug 18, 2015 at 11:14

answered Aug 18, 2015 at 9:35

Willi Mentzel

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Comments

Prabhjot Singh Chandhar · Accepted Answer · 2017-04-09 08:07:59Z

0

You can this way also. Just call split method on the String returned with comma

public String replaceNullSplitLine(String line){
    if(line.endsWith(",")){
        line = line+"***";
    }
    line = line.replaceAll(",,", ",***,");
    return line;
}

answered Apr 9, 2017 at 8:07

Prabhjot Singh Chandhar

1

Comments

Philipp Sander · Accepted Answer · 2015-08-18 09:14:20Z

-1

Check the length of the array before trying to use the last (and in that case non-existed) values

myArray.length

answered Aug 18, 2015 at 9:14

Philipp Sander

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