Java

How can I delete empty lines from file?

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Join Date: May 2007

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katerinaaa katerinaaa is offline

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How can I delete empty lines from file?

Jun 8th, 2007

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

 Help with Code Tags 
 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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Join Date: May 2007

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Ezzaral

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Re: How can I delete empty lines from file?

Jun 8th, 2007

 Help with Code Tags 
 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.

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~s.o.s~

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Re: How can I delete empty lines from file?

Jun 9th, 2007

> 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.

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Join Date: May 2008

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addiakogiannis addiakogiannis is offline

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Re: How can I delete empty lines from file?

May 2nd, 2008

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

 Help with Code Tags 
 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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Join Date: Aug 2007

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jasimp

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Re: How can I delete empty lines from file?

May 2nd, 2008

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

"Argyou not with the hand you are dealt in cards or life." ---- Wizard and Glass

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Ezzaral

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Re: How can I delete empty lines from file?

May 2nd, 2008

Not to mention that this while condition is just plain wrong

 Help with Code Tags 
 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.

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alpe gulay alpe gulay is offline

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just try!

May 6th, 2008

//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";
}

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Join Date: Aug 2007

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jasimp

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Re: just try!

May 6th, 2008

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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.

"Argyou not with the hand you are dealt in cards or life." ---- Wizard and Glass