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Java Discussion Thread
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Jun 8th, 2007

How can I delete empty lines from file?

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Hi,
I would like to ask if anyone knows how can I delete empty lines from a file.

I thought that I have to crate a loop like

Java Syntax (Toggle Plain Text)
FileInputStream fstream = new FileInputStream("input.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader (new InputStreamReader(in));
 
String strLine;
while(br.readline()!=null)
{
//....
}
FileInputStream fstream = new FileInputStream("input.txt");
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader (new InputStreamReader(in));
    
String strLine;
while(br.readline()!=null)
{
//....
}

But the program stops in the first null line.

Any ideas ?

Thanks

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katerinaaa

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Jun 8th, 2007

Re: How can I delete empty lines from file?

Java Syntax (Toggle Plain Text)
            BufferedReader br = new BufferedReader(new FileReader("c:/test.txt"));
            String strLine;
            while((strLine=br.readLine())!=null) {
                if (strLine.length()>0) System.out.println(strLine);
            }
            BufferedReader br = new BufferedReader(new FileReader("c:/test.txt"));
            String strLine;
            while((strLine=br.readLine())!=null) {
                if (strLine.length()>0) System.out.println(strLine);
            }

Of course, you will probably want to write those lines back out to a file instead of printing them to System.out.

Ezzaral

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Jun 9th, 2007

Re: How can I delete empty lines from file?

> But the program stops in the first null line.
null != empty_line

A null returned signifies that a end of file has been reached and has got nothing to do with empty lines. Inside your loop, just check to see if str.trim().length() != 0 and write that line to the target file.

~s.o.s~

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Failure as a human

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May 2nd, 2008

Re: How can I delete empty lines from file?

So you want to skip the empty lines correct?
Here you go....

java Syntax (Toggle Plain Text)
// command line parameter
FileInputStream fstream = new FileInputStream("myfile.txt");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
while ((line = br.readLine()) != null && !"".equals(line = br.readLine().trim()))   {
......
}
// command line parameter
FileInputStream fstream = new FileInputStream("myfile.txt");
// Get the object of DataInputStream
DataInputStream in = new DataInputStream(fstream);
BufferedReader br = new BufferedReader(new InputStreamReader(in));
while ((line = br.readLine()) != null && !"".equals(line = br.readLine().trim()))   {
......
}

Last edited by addiakogiannis; May 2nd, 2008 at 7:39 am.

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May 2nd, 2008

Re: How can I delete empty lines from file?

This thread is almost a year old. I doubt they still need help on it.

jasimp

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May 2nd, 2008

Re: How can I delete empty lines from file?

Not to mention that this while condition is just plain wrong

Java Syntax (Toggle Plain Text)
while ((line = br.readLine()) != null && !"".equals(line = br.readLine().trim()))   {
......
}
while ((line = br.readLine()) != null && !"".equals(line = br.readLine().trim()))   {
......
}

It will read two lines and test them separately. One will be tested for null and the second for an empty string. I don't think the goal is to process every other line in the file.

And it's a confusing mess to read. Try for clarity over being clever just to minimize the lines of code.

Last edited by Ezzaral; May 2nd, 2008 at 1:06 pm.

Ezzaral

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May 6th, 2008

just try!

//after declaring your filereader just put up this condition
BufferedReader reader = new BufferedReader(new FileReader("--your file here--"));
String line="";
String out="";
while((line=reader.readLine())!=null)
{
if (line.length()>0)
out+=line+"\n";
}

alpe gulay

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May 6th, 2008

Re: just try!

Click to Expand / Collapse Quote originally posted by alpe gulay ...

//after declaring your filereader just put up this condition
BufferedReader reader = new BufferedReader(new FileReader("--your file here--"));
String line="";
String out="";
while((line=reader.readLine())!=null)
{
if (line.length()>0)
out+=line+"\n";
}

Read before you post. We already stated the question was asked one year ago.

jasimp

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May 6th, 2008

Re: How can I delete empty lines from file?

.,sory poh!!!
i'm still beginners in this site..!
I took crelessness with this one...
hehehehe!!!dont get mad guys!

alpe gulay

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This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

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