How to count number of columns in CSV using Apache Commons CSV?

Question

How do I count the number of columns in a CSV file using Apache Commons CSV? My goal is to generate headers for the CSVParser, so long as I can determine the number of columns.

Example CSV file:

0,1,0
1,2,3
2,3,4
...

In this case the number of columns would be three. So what I'm looking for is something like:

CSVParser parser = format.parse(file);
CSVRecord firstRecord = parser.iterator().next();
int numColumns = firstRecord.size();

Note: I seem to be able to parse files just fine as long as they have an extra line at the beginning and I create a format, as such:

file:

asdf
0,1,0
1,2,3
2,3,4
...

format:

CSVFormat = format.withFirstRecordAsHeader().withSkipHeaderRecord()

score 3 · Answer 1 · answered Dec 07 '16 at 09:08

3

This is too late to answer & not sure on what version you are using. With Apache commonCSV 1.4 (JDK 6+), firstRecord.size() is available.

answered Dec 07 '16 at 09:08

Saurabhcdt

1,010
1
12
24

I actually did find an answer and just forgot to post it. Answer above. The problem with using firstRecord.size() is that commons CSV rejects the file when the header has too many columns or too few, and absolutely requires a header. – Gladclef Jan 08 '17 at 02:49

score 0 · Accepted Answer · answered Jan 08 '17 at 03:27

The solution I have found is to prepend a fake line before the contents of the file and use a format that slips the header record.

public static CSVParser getParserForUnknownCSV(FileInputStream inputStream)
{
    Byte[] fakeLine = ("fake line" + System.lineSeparator()).toByteArray();
    ByteArrayInputStream fakeLineStream = new ByteArrayInputStream(fakeLine);
    SequenceInputStream prependedStream = new SequenceInputStream(fakeLineStream, inputStream);
    InputStreamReader prependedReader = new InputStreamReader(prependedStream)

    CSVFormat formatWithFakeHeader = CSVFormat.DEFAULT
        .withSkipHeaderRecord()
        .withHeader("fake header")
        .withAllowMissingColumnNames();
    CSVParser parser = new CSVParser(prependedReader, formatWithFameHeader);

    return parser;
}

How to count number of columns in CSV using Apache Commons CSV?

2 Answers2