Count Line Numbers of File in Java

Question

I am trying to count line no. of a file using Java LineNumberReader. The output comes with problem. The problem is the alternative lines are displayed like line no. 1,3,5,... and on counting total no of lines i got half no. of the total actual lines. Here is the code

import java.lang.*;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.io.LineNumberReader;

public class countLine{
    File file=null;
    public countLine(){
            file =new File("E:\\test.txt");
        getFileData();
    }
    public void getFileData(){
            try{ 
                if(file.exists()){
                    FileReader fr = new FileReader(file);
                    LineNumberReader lnr = new LineNumberReader(fr); 
                    int linenumber = 0;
                        do{
                System.out.println(lnr.readLine());
                        linenumber++;
                        }while (lnr.readLine() != null);
                        System.out.println("Total number of lines : " + linenumber);
                        lnr.close();
                }else{
                     System.out.println("File does not exists!");
                }
            }
        catch(Exception e){
            e.printStackTrace();
        }   
    }   
    public static void main(String h[]){
        countLine cl = new countLine(); 
    }
}

line 1,3,5 and so on are printed. on counting total no. of lines for ex. there are 10 lines then in output i get only 5 — Harsh Kanakhara, Dec 31 '14 at 16:05

Michal · Answer 1 · 2014-12-31T16:36:13.830

7

You read the line twice, once with System.out.println(lnr.readLine()); and once with while (lnr.readLine() != null);

Combining the two other answers into one gives correct line count as well as the ability of doing the System.out.println(...) with line content:

int linenumber = 0;
String tmp = new String();
while ((tmp = lnr.readLine()) != null) {
    linenumber++;
    System.out.println(tmp);
}

edited Dec 31 '14 at 16:36

answered Dec 31 '14 at 16:03

Michal

2,353
1
15
18

what is the proper way ? – Harsh Kanakhara Dec 31 '14 at 16:06
As one of the other answers suggested, depending on the fact whether you need the System.out.println of line content (Naor's answer) or not (laune's answer). – Michal Dec 31 '14 at 16:14
Yeah, that's ok. In my understanding your original code had one more bug, the do-while counted one line too much, if I see it correctly. But I did not unit-tested that assumption. – Michal Dec 31 '14 at 16:18
I am sorry I was too fast embracing the two answers. Naor's answer counts one line too much, you would need to initialize the linenumber with -1. – Michal Dec 31 '14 at 16:33

laune · Answer 2 · 2014-12-31T16:41:57.517

0

This would have been enough for counting:

FileReader fr = new FileReader(file);
LineNumberReader lnr = new LineNumberReader(fr); 
while (lnr.readLine() != null);
System.out.println( lnr.getLineNumber() );
lnr.close();

Added later Or, if you need to print lines (+ line numbers):

String line = null;
while ((line = lnr.readLine()) != null){
    System.out.println( lnr.getLineNumber() + " " +  lnr.getLineNumber() );
}

edited Dec 31 '14 at 16:41

answered Dec 31 '14 at 16:08

laune

31,114
3
29
42

thanks..but what to do if i want to print content of that line number – Harsh Kanakhara Dec 31 '14 at 16:11

score 0 · Answer 3 · answered Jan 01 '15 at 09:06

0

You can get the number of lines with two lines of code: something like

lineNumberReader.skip(Long.MAX_VALUE);
int count = LineNumberReader.getLineNumber();

E&OE

answered Jan 01 '15 at 09:06

user207421

305,947
44
307
483

Naor88 · Accepted Answer · 2018-01-10T16:31:55.203

-1

Every lnr.readLine() read a line from the file and return it.
You are making two reads:
1)At the System.out.println
2)At the while statement

You need make a call to readLine method,
save the result at variable and when it a null is the end of the file.

Take a look at:

int linenumber = 0;
String tmp = new String();
while ((tmp = lnr.readLine()) != null) {
    linenumber++;
    System.out.println(tmp);
}

edited Jan 10 '18 at 16:31

answered Dec 31 '14 at 16:26

Naor88

50
1
8

1

Why are you initializing `tmp` When it's assigned in the very next line? And what does 'if the file empty it's not count!!!' mean? And how many times are you going to answer this question? – user207421 Jan 01 '15 at 09:08
I'm rewrite my previous answer, it really don't be so understood sorry for that.. :) – Naor88 Jan 10 '18 at 16:36

Count Line Numbers of File in Java

4 Answers4