Replace a particular String from a text file

Question

I'm trying to replace the occurence of a certain String from a given text file. Here's the code I've written:

BufferedReader tempFileReader = new BufferedReader(new InputStreamReader(new FileInputStream(tempFile)));
File tempFileBuiltForUse = new File("C:\\testing\\anotherTempFile.txt");
Writer changer = new BufferedWriter(new FileWriter(tempFileBuiltForUse));
String lineContents ;
while( (lineContents = tempFileReader.readLine()) != null)
{
    Pattern pattern = Pattern.compile("/.");
    Matcher matcher = pattern.matcher(lineContents);
    String lineByLine = null;
    while(matcher.find())
    {
        lineByLine = lineContents.replaceAll(matcher.group(),System.getProperty("line.separator"));
        changer.write(lineByLine);
    }
}
changer.close();
tempFileReader.close();

Suppose the contents of my tempFile are:

This/DT is/VBZ a/DT sample/NN text/NN ./.

I want the anotherTempFile to contain :

This/DT is/VBZ a/DT sample/NN text/NN . with a new line.

But I'm not getting the desired output. And I'm not able to see where I'm going wrong. :-( Kindly help. :-)

devsnd · Accepted Answer · 2012-03-13 16:06:35Z

3

A dot means "every character" in regular expressions. Try to escape it:

Pattern pattern = Pattern.compile("\\./\\.");

(You need two backslahes, to escape the backslash itself inside the String, so that Java knows you want to have a backslash and not a special character as the newline character, e.g. \n

edited Mar 13, 2012 at 16:06

answered Mar 13, 2012 at 15:59

devsnd

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2 Comments

Kazekage Gaara Over a year ago

Much better. But now, the output generated is every word in newline. Still not what I want.

Kazekage Gaara Over a year ago

Just a minor edit, for the pattern to be matched. Just for /. it'll be the same thing you suggested before?

Tim Pietzcker · Accepted Answer · 2012-03-13 16:01:25Z

2

In a regex, the dot (.) matches any character (except newlines), so it needs to be escaped if you want it to match a literal dot. Also, you appear to be missing the first dot in your regex since you want the pattern to match ./.:

Pattern pattern = Pattern.compile("\\./\\.");

answered Mar 13, 2012 at 16:01

Tim Pietzcker

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Comments

Drona · Accepted Answer · 2012-03-13 16:08:58Z

Your regular expression has a problem. Also you don't have to use the Pattern and matcher. Simply use replaceAll() method of the String class for the replacement. It would be easier. Try the code below:

        tempFileReader = new BufferedReader(
                new InputStreamReader(new FileInputStream("c:\\test.txt")));
        File tempFileBuiltForUse = new File("C:\\anotherTempFile.txt");
        Writer changer = new BufferedWriter(new FileWriter(tempFileBuiltForUse));
        String lineContents;
        while ((lineContents = tempFileReader.readLine()) != null) {
            String lineByLine = lineContents.replaceAll("\\./\\.", System.getProperty("line.separator"));
            changer.write(lineByLine);
        }
        changer.close();
        tempFileReader.close();

korifey · Accepted Answer · 2012-03-13 16:03:23Z

1

/. is a regular expression \[any-symbol]. Change into to `/\\.'

answered Mar 13, 2012 at 16:03

korifey

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