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getting # of lines in file

Posted on 2004-03-28
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Last Modified: 2010-03-31
hello, how can i get the number of lines in a text file without looping though the lines?
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Question by:91mustang
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by:CEHJ
ID: 10699253
You can't really. Why would you want to though?
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by:91mustang
ID: 10699258
I have an app that reads a file in line parses line, inserts to DB,next line....

I want to use a Jprogress bar and use the number of lines in file as the maximum value for proggress bar
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Accepted Solution

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CEHJ earned 20 total points
ID: 10699282
You could do something like this:


import java.util.regex.*;
import java.nio.*;
import java.nio.charset.*;
import java.nio.channels.*;
import java.io.*;

/**
 *  Description of the Class
 *
 * @author     CEHJ
 * @created    28 March 2004
 */
public class LineCount2 {

      public static void main(String[] args) throws Exception {
            if (args.length < 1) {
                  System.out.println("Usage: java LineCount2 <text file to count lines of>");
                  System.exit(-1);
            }
            int count = 0;
            FileChannel roChannel = new RandomAccessFile(new File(args[0]), "r").getChannel();
            ByteBuffer bbuf = roChannel.map(FileChannel.MapMode.READ_ONLY, 0, (int) roChannel.size());
            CharBuffer cbuf = Charset.forName(System.getProperty("file.encoding")).newDecoder().decode(bbuf);

            Pattern EOL = Pattern.compile("\\n");
            Matcher matcher = EOL.matcher(cbuf);
            while (matcher.find()) {
                  count++;
            }
            if (cbuf.length() > 0) {
                  ++count;
            }
            System.out.println(count + " lines found");
      }

}
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Expert Comment

by:twobitadder
ID: 10699284
You'll need to do a pre-parse/dbInsertion parse to compare every character for '/n' and sum them.
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Author Comment

by:91mustang
ID: 10699508
thanks CEHJ
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Expert Comment

by:CEHJ
ID: 10699524
8-)
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