Reading multiple CSV files

[Akil Kumar]

Hello,

I have data in a CSV (Comma separated value) file and I read that text file from the client in Java. The purpose behind this is to create a mock dataset for the client. Is it possible to read multiple CSV files and update the client with different data sets? Right now I use buffered reader and file reader to read the file and String Tokenizer to read the individual tokens within the file. Can anyone tell if the above scenario is possible? Please.

Thanks,

[Philip Grove]

Reading multiple files regardless of format is perfectly doable, you just have to make sure not to overwrite "old" data when reading new files.

Using StringTokenizer is strongly discouraged, it's a legacy class retained for compatability reasons. Look into the split() methods of String or the java.util.regex package. While regular expressions might be difficult at first, and more so in Java as they don't use the standard POSIX syntax, it's a very powerful tool.

If you want a object doing the splitting, then look at the Scanner class of the java.util package, it does support having a String as a source.

[Joe Areeda]

I've been using a package called opencsv (http://opencsv.sourceforge.net/).

The different tokenizers are fine if the data is simple but if you're dealing with spreadsheets or databases it can get complicated.

Things like quoted or escaped commas are not that easy to deal with:
"Smith,John", senior
Tom\, Dick\, and Harry, idiom

As far as the multiple files, like Phillip I don't see the issue. What are concerned about?

Joe

[Akil Kumar]

Philip Grove wrote:Reading multiple files regardless of format is perfectly doable, you just have to make sure not to overwrite "old" data when reading new files.

Using StringTokenizer is strongly discouraged, it's a legacy class retained for compatability reasons. Look into the split() methods of String or the java.util.regex package. While regular expressions might be difficult at first, and more so in Java as they don't use the standard POSIX syntax, it's a very powerful tool.

If you want a object doing the splitting, then look at the Scanner class of the java.util package, it does support having a String as a source.

Hello,

Thanks for the reply. I have the following code to read the CSV file. Can you explain what you are saying with some code sample? Do you want loop through all files?
My delimiter in this case is space " ".

String strFile = "C:/Users/Data.csv";

BufferedReader br = new BufferedReader(new FileReader(strFile));
String strLine = "";
StringTokenizer st = null;
int lineNumber = 0;
int numbers[][] = new int[120][2];

//pretend you're looping through lines in a file here
while((strLine = br.readLine()) != null)
{
lineNumber++;

//break space separated line using " "
st = new StringTokenizer(strLine, " ");

while(st.hasMoreTokens())
{
//display echo values
int data1 = Integer.parseInt(st.nextToken());
numbers[lineNumber][0] = data1;

int data2 = Integer.parseInt(st.nextToken());
numbers[lineNumber][1] = data2;

System.out.println("Data1=" + data1 + " Data2=" + data2);

}

}

[Joe Areeda]

How about something like:

String[] fileNames = {"C:/Users/Data.csv", "C:/Users/Data2.csv", "C:/Users/Data3.csv};
for(String strFile : fileNames)
{
   BufferedReader br = new BufferedReader(new FileReader(strFile)); 
   ...<process the file>...
   br.close();
}

Joe

[Ulf Dittmer]

I generally advise to use one of the numerous available CSV libraries instead of rolling your own (see the AccessingFileFormats page for a list of such libraries). CSV has features that will break the code you posted.