Replace a character in a BufferedWriter

Question

I am creating a text file using BufferedWriter

BufferedWriter bufferedWriter = 
           new BufferedWriter(new FileWriter("/home/user/temp.txt"));

/*

     Add Contents using bufferedWriter.write()

*/

At certain places while adding contents I add a string sequence ######

Before I do bufferedWriter.close() I want to replace the ###### sequence with some specific value.

How can I do that?

I do not want to re-open the Writer, but could use a different writer if it allows this to be done.

Why do you write it if you're just going to replace it? Is it like a template? — Sotirios Delimanolis, Feb 12 '13 at 18:59
See [`RandomAccessFile`](http://docs.oracle.com/javase/7/docs/api/java/io/RandomAccessFile.html). — Eng.Fouad, Feb 12 '13 at 19:00
@SotiriosDelimanolis The value that has to be replaced is only known after certain calculations and only once the contents are put in. — Sangeet Menon, Feb 12 '13 at 19:07

score 2 · Answer 1 · answered Feb 12 '13 at 19:03

2

Create the contents as a String or a List<String>.

After you replace the #####, you write the String or List<String> to the BufferedWriter.

answered Feb 12 '13 at 19:03

Gilbert Le Blanc

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Petr Janeček · Answer 2 · 2013-06-05T20:27:45.747

I believe you have the following options:

Write your own Writer. None of the Writers I know about are able to do this simply because they actually write to disk (into the file) when you call .write() on them. Some, like BufferedWriter, don't do it immediatelly, but if you exceed the inner buffer, it will be flushed into the file anyway - even without you calling flush() or close().
Simply use StringBuilder. Write to a StringBuilder, then replace your sequence and only then write to a file.
Write to a new file every time you encounter ######. Effectively, you'll have several files with a missing piece of text in between them. After you know the right sequence that should replace ######, join the files using that sequence.
If you have enough memory to hold all the data in memory, use a List<String> (split at the ######, then join the elements using something like a Joiner).

score -1 · Answer 3 · answered Feb 12 '13 at 19:14

What about something like that ?

BufferedReader br = new BufferedReader(new FileReader("/home/user/temp.txt"));
BufferedWriter bw = new BufferedWriter(new FileWriter("/home/user/temp.txt"))
String line
StringBuffer sb = new StringBuffer()
while (line = br.readLine()) {
    line = line.replace("######", "yourReplacement")
    sb.append(line)
}
br.close()
bw.write(sb.toString(), 0, sb.length())
bw.close()

Replace a character in a BufferedWriter

3 Answers3