Splitting a CSV File with Quotes as Text-Delimiter Using String.Split()

Splitting a csv file with quotes as text-delimiter using String.split()

public static void main(String[] args) {
    String s = "Sachin,,M,\"Maths,Science,English\",Need to improve in these subjects.";
    String[] splitted = s.split(",(?=([^\"]*\"[^\"]*\")*[^\"]*$)");
    System.out.println(Arrays.toString(splitted));
}

Output:

[Sachin, , M, "Maths,Science,English", Need to improve in these subjects.]

Java: splitting a comma-separated string but ignoring commas in quotes

Try:

public class Main { 
    public static void main(String[] args) {
        String line = "foo,bar,c;qual=\"baz,blurb\",d;junk=\"quux,syzygy\"";
        String[] tokens = line.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)", -1);
        for(String t : tokens) {
            System.out.println("> "+t);
        }
    }
}

Output:

> foo
> bar
> c;qual="baz,blurb"
> d;junk="quux,syzygy"

In other words: split on the comma only if that comma has zero, or an even number of quotes ahead of it.

Or, a bit friendlier for the eyes:

public class Main { 
    public static void main(String[] args) {
        String line = "foo,bar,c;qual=\"baz,blurb\",d;junk=\"quux,syzygy\"";
        
        String otherThanQuote = " [^\"] ";
        String quotedString = String.format(" \" %s* \" ", otherThanQuote);
        String regex = String.format("(?x) "+ // enable comments, ignore white spaces
                ",                         "+ // match a comma
                "(?=                       "+ // start positive look ahead
                "  (?:                     "+ //   start non-capturing group 1
                "    %s*                   "+ //     match 'otherThanQuote' zero or more times
                "    %s                    "+ //     match 'quotedString'
                "  )*                      "+ //   end group 1 and repeat it zero or more times
                "  %s*                     "+ //   match 'otherThanQuote'
                "  $                       "+ // match the end of the string
                ")                         ", // stop positive look ahead
                otherThanQuote, quotedString, otherThanQuote);

        String[] tokens = line.split(regex, -1);
        for(String t : tokens) {
            System.out.println("> "+t);
        }
    }
}

which produces the same as the first example.

EDIT

As mentioned by @MikeFHay in the comments:

I prefer using Guava's Splitter, as it has saner defaults (see discussion above about empty matches being trimmed by String#split(), so I did:

Splitter.on(Pattern.compile(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)"))

Splitting a CSV File in Java that has extra commas and extra quotes in them

Thanks to Andreas and Tamas Hegedus for helping you clarify the question! Try:

        br = new BufferedReader(new FileReader(customerListAllCustomers));
        while ((line = br.readLine()) != null) {
            // one column, so don't need to use comma as separator
            String line2 = line.replaceAll("^\"","").replaceAll("\"$","").replaceAll("\\\"","\"");
            System.out.println(line2);

The replaceAll calls strip leading quotes (^\") and trailing quotes (\"$), and then unescape the remaining quotes (\\\").

split a comma-separated string with both quoted and unquoted strings

Depending on your needs you may not be able to use a csv parser, and may in fact want to re-invent the wheel!!

You can do so with some simple regex

(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)

This will do the following:

(?:^|,) = Match expression "Beginning of line or string ,"

(\"(?:[^\"]+|\"\")*\"|[^,]*) = A numbered capture group, this will select between 2 alternatives:

1. stuff in quotes
2. stuff between commas

This should give you the output you are looking for.

Example code in C#

 static Regex csvSplit = new Regex("(?:^|,)(\"(?:[^\"]+|\"\")*\"|[^,]*)", RegexOptions.Compiled);

public static string[] SplitCSV(string input)
{

  List<string> list = new List<string>();
  string curr = null;
  foreach (Match match in csvSplit.Matches(input))
  {        
    curr = match.Value;
    if (0 == curr.Length)
    {
      list.Add("");
    }

    list.Add(curr.TrimStart(','));
  }

  return list.ToArray();
}

private void button1_Click(object sender, RoutedEventArgs e)
{
    Console.WriteLine(SplitCSV("111,222,\"33,44,55\",666,\"77,88\",\"99\""));
}

Warning As per @MrE's comment - if a rogue new line character appears in a badly formed csv file and you end up with an uneven ("string) you'll get catastrophic backtracking (https://www.regular-expressions.info/catastrophic.html) in your regex and your system will likely crash (like our production system did). Can easily be replicated in Visual Studio and as I've discovered will crash it. A simple try/catch will not trap this issue either.

You should use:

(?:^|,)(\"(?:[^\"])*\"|[^,]*)

instead

How to split csv whose columns may contain comma

Use the Microsoft.VisualBasic.FileIO.TextFieldParser class. This will handle parsing a delimited file, TextReader or Stream where some fields are enclosed in quotes and some are not.

For example:

using Microsoft.VisualBasic.FileIO;

string csv = "2,1016,7/31/2008 14:22,Geoff Dalgas,6/5/2011 22:21,http://stackoverflow.com,\"Corvallis, OR\",7679,351,81,b437f461b3fd27387c5d8ab47a293d35,34";

TextFieldParser parser = new TextFieldParser(new StringReader(csv));

// You can also read from a file
// TextFieldParser parser = new TextFieldParser("mycsvfile.csv");

parser.HasFieldsEnclosedInQuotes = true;
parser.SetDelimiters(",");

string[] fields;

while (!parser.EndOfData)
{
    fields = parser.ReadFields();
    foreach (string field in fields)
    {
        Console.WriteLine(field);
    }
} 

parser.Close();

This should result in the following output:

2
1016
7/31/2008 14:22
Geoff Dalgas
6/5/2011 22:21
http://stackoverflow.com
Corvallis, OR
7679
351
81
b437f461b3fd27387c5d8ab47a293d35
34

See Microsoft.VisualBasic.FileIO.TextFieldParser for more information.

You need to add a reference to Microsoft.VisualBasic in the Add References .NET tab.

Delimit a string by character unless within quotation marks C#

Copied from my comment: Use an available csv parser like VisualBasic.FileIO.TextFieldParser or this or this.

As requested, here is an example for the TextFieldParser:

var allLineFields = new List<string[]>();
string sampleText = "Method,\"value1,value2\"";
var reader = new System.IO.StringReader(sampleText);
using (var parser = new Microsoft.VisualBasic.FileIO.TextFieldParser(reader))
{
    parser.Delimiters = new string[] { "," };
    parser.HasFieldsEnclosedInQuotes = true; // <--- !!!
    string[] fields;
    while ((fields = parser.ReadFields()) != null)
    {
        allLineFields.Add(fields);
    }
}

This list now contains a single string[] with two strings. I have used a StringReader because this sample uses a string, if the source is a file use a StreamReader(f.e. via File.OpenText).

Split string on comma and ignore comma in double quotes

I think you can use the regex,(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$) from here: Splitting on comma outside quotes

You can test the pattern here: http://regexr.com/3cddl

Java code example:

public static void main(String[] args) {
    String txt = "0, 2, 23131312,\"This, is a message\", 1212312";

    System.out.println(Arrays.toString(txt.split(",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)")));

}

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