Solved

Java parsing, better way to use tokenizer?

Posted on 2007-11-23
10
1,018 Views
Last Modified: 2008-09-20
I'm trying to parse a csv file (probably made in excel, or access).

Each field is separated by a "," (comma) but some fields are empty, so I'm not getting the data correctly.

Below is what I'm doing now. Is there a better way to parse?


This line works fine:
23, something, aTitle, something, Smith

This line gives me wrong values:

21,,anotherTitle,,Jones

Both come from the same table with 4 fields.

Thanks.
//...			

String line = in.readLine();

while(line!=null)

{

	StringTokenizer st = new StringTokenizer(line,",");

	int fieldCount=0;

			

	while(st.hasMoreTokens())

	{

		String nextFieldData = st.nextToken();

		++fieldCount;

				

					

		switch(fieldCount)

		{

			case 1: 

			String ID = (nextFieldData);

			break;

						

			case 3: 

			String Title  = (nextFieldData);

			break;
 

			case 5: 

			String Name  = (nextFieldData);

			break;

		}

//...

Open in new window

0
Comment
Question by:polkadot
10 Comments
 
LVL 26

Expert Comment

by:ksivananth
ID: 20339104
there are lot of issues which you have to take care if you do it that ways...

instead try some readily available parsers,

http://opencsv.sourceforge.net/
http://www.csvreader.com/
0
 

Author Comment

by:polkadot
ID: 20339344
csvreader works great, but its a bit bulky, I just wanted some ideas in just parsing it simply ... any other ideas
0
 
LVL 27

Expert Comment

by:mrcoffee365
ID: 20339554
Then you can't use StringTokenizer, you have to write your own parser.  Read the line character by character, check to see if there's a comma, and parse accordingly.
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 20339614
http://ostermiller.org/utils/CSV.html

I would not use home-brewed parsing. If it were that simple, there would not be any need for classes such as these
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 26

Expert Comment

by:ksivananth
ID: 20339620
>>StringTokenizer st = new StringTokenizer(line,",");

to

StringTokenizer st = new StringTokenizer( line,",", true );

and discard the odd( which is the comma ) tokens in the traversing process...
0
 
LVL 92

Expert Comment

by:objects
ID: 20340802
you can find a lightweight csv parser here:

http://mindprod.com/zips/csv24.zip
0
 
LVL 16

Accepted Solution

by:
gnoon earned 500 total points
ID: 20344564
I've surveyed the source code of ST. If delemeters are successive (having blank field(s)), they will be group as a delemeter. For example

data: 1,,3,   will become   1,3,   (ST acts with ,, as ,)
return: {1,3,}

ST is not appropriate to parse CSV file.
If you will use JRE 1.4+, use String.split() instead    String[] fields = line.split(",").
If you will use JRE 1.3-, write your own function to parse the line (never use StringTokenizer) and returns array of fields.
0
 
LVL 16

Expert Comment

by:gnoon
ID: 20344587
public String[] parse(String s, char delim)
{
    StringBuffer b = new StringBuffer();
    ArrayList a = new ArrayList();
    char c;
    for(int i=0; i<s.length(); i++)
    {
        c = s.charAt(i);
        if(c == delim)
        {
            a.add(b);
            b = new StringBuffer();
        }
        else b.append(c);
    }
    String[] r = new String[a.size()];
    for(int i=0; i<r.length; i++)
        r[i] = (String) a.get(i);
    return r;
}
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

INTRODUCTION Working with files is a moderately common task in Java.  For most projects hard coding the file names, using parameters in configuration files, or using command-line arguments is sufficient.   However, when your application has vi…
Java contains several comparison operators (e.g., <, <=, >, >=, ==, !=) that allow you to compare primitive values. However, these operators cannot be used to compare the contents of objects. Interface Comparable is used to allow objects of a cl…
Video by: Michael
Viewers learn about how to reduce the potential repetitiveness of coding in main by developing methods to perform specific tasks for their program. Additionally, objects are introduced for the purpose of learning how to call methods in Java. Define …
The viewer will learn how to implement Singleton Design Pattern in Java.

895 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

17 Experts available now in Live!

Get 1:1 Help Now