I've found a bunch of similiar questions there, but all the proposed solutions already exist in my code, so...
I have the following routine being called from different places in my app:
static private void writeToFile(String data) {
File file = new File("sdcard/output.txt");
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
BufferedWriter bw = null;
try {
FileWriter fw = new FileWriter(file, true);
bw = new BufferedWriter(fw);
bw.append(new Date().toString() + " " + data);
bw.newLine();
}
catch (IOException e) {
e.printStackTrace();
}
finally {
try {
if(bw != null) {
bw.close();
}
} catch(Exception e) {
e.printStackTrace();
}
}
}
Sometimes after a while strings stop to be added to a file. I've presumed it's something about syncronization - but once I've succeeded to catch it in debug mode and stepped all over the routine - every statement is executed without any exceptions.
Can you, please, tell what's wrong with my code?
Related
Came across the below code from a Java book
public void writeFile(String fileName, String content){
File file = new File(fileName);
try {
try (PrintWriter output = new PrintWriter(new FileWriter(file))) {
output.println(content);
output.println();
output.println("End of writing");
}
System.out.println("File been written successfully");
} catch (IOException ex) {
ex.printStackTrace(System.out);
}
}
Nothing is wrong with the above code, I simply couldn't see the point of having a nested try that doesn't define an inner catch block. Or is there any purpose of doing so in which I've missed it?
Revised code:
public void writeFile(String fileName, String content){
File file = new File(fileName);
try (PrintWriter output = new PrintWriter(new FileWriter(file))) {
output.println(content);
output.println();
output.println("End of writing");
System.out.println("File been written successfully");
} catch (IOException ex) {
ex.printStackTrace(System.out);
}
}
The inner try is a try-with-resources:
try (PrintWriter output = new PrintWriter(new FileWriter(file)))
it means, that it manages the resource - PrintWriter - opens it and closes it after every statement in this try is conducted. The outer try is used to catch the error.
Your revised code what Petter Friberg proposed, is equivalent.
I would like to make you think about a tiny problem using the method printStackTrace(PrintWriter s). I need to use it in append mode.
The following example is explaining what I mean:
try {
} catch (Exception e) {
try {
e.printStackTrace(new PrintWriter(new FileWriter("mylog.txt", true)));
} catch (IOException ioe) {
System.out.println("I can't open the file mylog.txt");
}
}
Note that
new FileWriter("mylog.txt", true);
is the way I open the file (and create it the first time because it doesn't exist) in append mode.
The result is that in the file there is only the last exception and not a series of exceptions. One time it occurred that the method opened the file in which it didn't write anything.
How can I solve this problem?
Thank you.
Adding to what krzyk mentioned
Per OutputStreamWriter.close() : Closes the stream, flushing it first. Once the stream has been closed, further write() or flush() invocations will cause an IOException to be thrown. Closing a previously closed stream has no effect.
As mentioned, if you do not call close and this try{}catch is getting fired frequently, you are not flushing content to file.
It should written like
try {
} catch (Exception e) {
try {
FileWriter fw = new FileWriter("mylog.txt", true)
e.printStackTrace(new PrintWriter(fw));
fw.close();
} catch (IOException ioe) {
System.out.println("I can't open the file mylog.txt");
}
}
A better approach will be
FileWriter fw = new FileWriter("mylog.txt", true);
PrintWriter pw = new PrintWriter(fw);
try {
} catch (Exception e) {
try {
e.printStackTrace(pw);
} catch (IOException ioe) {
System.out.println("I can't open the file mylog.txt");
}
}finally {
pw.close();
fw.close();
}
You should close the created Writers, not closing it might cause the problems you describe.
try (PrintWriter writer = new PrintWriter(new FileWriter("mylog.txt", true))) {
e.printStackTrace(writer);
}
I'm trying to close a RandomAccessFile but resource remain busy.
Code:
public boolean isOpen(RandomAccessFile f) {
try {
f.length() ;
return true ;
}
catch (IOException e) {
return false ;
}
}
this.rfmFile = new File(filePath);
try {
this.rfmRandomAccessFile = new RandomAccessFile(rfmFile, "rws");
} catch(Exception e){
}finally{
this.rfmRandomAccessFile.close();
}
while(!isOpen(this.rfmRandomAccessFile));
log.debug("I Finally Closed this RAF");
Log is not showed and thread goes in loop.
When I try to access to my resource from shell it gives me "Device or Resource busy".
The only way to access is kill java process.
When you are trying to access the RandomAccessFile length(), method, it is already closed and thus you cannot access it anymore.
You probably want to use the length() method of File. Your loop cannot work as the RandomAccessFile was already closed.
But I must admit I am clueless on the low level reason why rfmRandomAccessFile would not really be closed. It could be a side effect of your strange loop trying to get the size of a closed file.
[edit:]Could not reproduce your issue with the following piece of code:
package com.company;
import java.io.*;
public class Main {
public static void main(String[] args) {
File file = new File("foobar.txt");
RandomAccessFile randomAccessFile = null;
try {
randomAccessFile = new RandomAccessFile(file, "rws");
randomAccessFile.write(new byte[]{'f'});
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(randomAccessFile !=null){
try {
randomAccessFile.close();
} catch (IOException e) {
//doh!
}
}
}
FileReader reader = null;
try {
reader = new FileReader(file);
char read = (char) reader.read();
System.out.println("what was written: "+read);
System.out.println("file size: "+file.length());
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(reader !=null){
try {
reader.close();
} catch (IOException e) {
//doh!
}
}
}
}
}
So, I have a function that reads file data, in this case image size. But after it's done it doesn't seem to properly release the files. I can't move those files afterwards. If I don't call this function everything works, but if I do I always get "file in use.. blah blah blah"
private void setMoveType() {
ImageInputStream in = null;
try {
in = ImageIO.createImageInputStream(new FileInputStream(file.toString()));
try {
final Iterator<ImageReader> readers = ImageIO.getImageReaders(in);
if(readers.hasNext()) {
ImageReader reader = readers.next();
try {
reader.setInput(in);
try {
moveType = Helper.getMoveType(new Dimension(reader.getWidth(0), reader.getHeight(0)));
} catch (IOException e) {
System.err.println("IOException: " + e.getMessage());
return;
}
} catch(Exception e) {
System.err.println("ReaderException: " + e.getMessage());
} finally {
reader.dispose();
}
}
} catch(Exception e) {
System.err.println("MoveTypeSetException: " + e.getMessage());
}
} catch (IOException e) {
System.err.print("IOException: failure while creating image input stream");
System.err.println(" -> createImageInputStream Error for file: " + file.getFileName());
return;
} finally {
if(in != null) {
try {
in.close();
} catch (IOException e) {
System.err.println("IOException: " + e.getMessage());
return;
}
}
}
}
EDIT: The ImageInputStream doesn't close properly
EDIT2: a FileInputStream wasn't closed
This stream should also be closed:
new FileInputStream(file.toString())
Closing the stream when you are done should work (in.close()). The operating system prevents the file from being changed, deleted or moved while it is in use. Otherwise, the stream would get messed up. Closing the stream tells the operating system you are no longer using the file.
I need to delete the contents of a file, before I write more information into it. I've tried different ways, such as where I delete the content but the file stays the same size, and when I start writing in it after the deletion, a blank hole appears to be the size of the deletion before my new data is written.
This is what I've tried...
BufferedWriter bw;
try {
bw = new BufferedWriter(new FileWriter(path));
bw.write("");
bw.close();
}
catch (IOException e) {
e.printStackTrace();
}
And I've also tried this...
File f = new File(file);
FileWriter fw;
try {
fw = new FileWriter(f,false);
fw.write("");
}
catch (IOException e) {
e.printStackTrace();
}
Can someone please help me with a solution to this problem.
FileWriter (path, false)
The false will tell the writer to truncate the file instead of appending to it.
Try calling flush() before calling close().
FileWriter writer = null;
try {
writer = ... // initialize a writer
writer.write("");
writer.flush(); // flush the stream
} catch (IOException e) {
// do something with exception
} finally {
if (writer != null) {
writer.close();
}
}
It might be because you are not closing the FileWriter, fw.close(); also you dont need to "delete" the old data, just start writing and it will overwrite the old data. So make sure you are closing everywhere.
This works for me:
File f=new File(file);
FileWriter fw;
try {
fw = new FileWriter(f);
fw.write("");
fw.close();
} catch (IOException e) {
e.printStackTrace();
}