PrintWriter to append data if file exist
Once you call PrintWriter out = new PrintWriter(savestr);
the file is created if doesn't exist hence first check for file existence then initialize it.
As mentioned in it's Constructor Docmentation as well that says:
If the file exists then it will be truncated to zero size; otherwise, a new file will be created.
Since file is created before calling f.exists()
hence it will return true
always and ìf
block is never executed at all.
Sample code:
String savestr = "mysave.sav";
File f = new File(savestr);
PrintWriter out = null;
if ( f.exists() && !f.isDirectory() ) {
out = new PrintWriter(new FileOutputStream(new File(savestr), true));
}
else {
out = new PrintWriter(savestr);
}
out.append(mapstring);
out.close();
For better resource handling use Java 7 - The try-with-resources Statement
TheWaveLad
Student, especially interested in Image Processing, Numerical Analysis, Discrete and Numerical Optimization and Data Fusion Mathematics.
Updated on June 27, 2022Comments
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TheWaveLad almost 2 years
I have a savegame file called
mysave.sav
and I want to add data to this file if the file already exists. If the file doesn't exists, I want to create the file and then add the data.Adding data works fine. But appending data overwrites existing data. I followed the instructions of axtavt here (PrintWriter append method not appending).
String savestr = "mysave.sav"; File f = new File(savestr); PrintWriter out = new PrintWriter(savestr); if ( f.exists() && !f.isDirectory() ) { out = new PrintWriter(new FileOutputStream(new File(savestr), true)); out.append(mapstring); out.close(); } else { out.println(mapstring); out.close(); }
where
mapstring
is the string I want to append. Can you help me? Thank you! -
TheWaveLad almost 10 yearsThank you, this works if I leave out the first line of the if block (out = new PrinterWriter(savestr)). I don't know if I'm allowed to edit your answer.
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Braj almost 10 years@pilky02 by mistake added. you are free to edit it. I am more than happy if you edit it.
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Braj almost 10 yearsThanks for edit. please follow last link that might help you a lot.