Develop Reference

Writing to file in java - close or flush

I'm writing a logger to my java program (in csv format) with bufferedWriter and FileWriter.
When i open the csv file while the program is running and continues writing to the file, I got this exception: "The process cannot access the file because it is being used by another process".
What i want is when i open the csv file while the program is running, The csv file will open in read mode and the program will writing successfully to the file.
I solved it by changing the closing of bufferedWriter and FileWriter to .flush() instead of .close()
Original minimal logger code (with the original close function)
public class logger {
private BufferedWriter bw = null;
private FileWriter fw = null;
private File file = null;
logger(String nclass) {
path = "c:\\test\\test.csv";
this.file = new File(path);
// Check if the file is already exist.
if (!file.exists()) {
file.createNewFile();
}
fw = new FileWriter(file.getAbsoluteFile(), true);
bw = new BufferedWriter(fw);
}
public void writeToFile(String msg) {
entryWrite();
try {
fw = new FileWriter(file.getAbsoluteFile(), true);
bw = new BufferedWriter(fw);
fw.append(msg);
} catch (IOException e) {
e.printStackTrace();
} finally {
close();
exitWrite();
}
}
}
private void close() {
try {
if (bw != null) {
bw.close();
bw = null;
}
if (fw != null) {
fw.close();
fw = null;
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
My solution function
private void close() {
try {
if (bw != null) {
bw.flush();
bw = null;
}
if (fw != null) {
fw.flush();
fw = null;
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
Now my answer is if it is ok not to close the stream and just use with flush?
Can there be any problems later? Because in all my tests its run well.
Thanks !!

Would it be ok some honesty?, in a very humble way. Sorry but stinky code:
why setting to null "bw" and "fw"?, globals?, why?
"ex.printStackTrace();" ? really?, no log4j or alike?
why not using a finally block?, what happens if an exception occurs while reading writing the file?
Someone has already answered this, for code refer to this excellent answer:
Is it necessary to close a FileWriter, provided it is written through a BufferedWriter?

Just do bufferedWriter object close.
bw.close();
say, you have a large file.txt.
Now u are gonna take something from a file and make a new smaller text file each time.
in that case,
somehow you have to write some lines of code to determine when you finish writing on a particular file. Then use flag to write bw.close();
eventually, you have to initialize the second file and do your task. then bw.close();
if you don't write fw.close(), then the file will be empty.
so, make sure each file writing operation you have to write bw.close()

Android BufferedWriter : Empty File Saved.

I am facing a problem and unable to identify it. The case is, I have an activity from which I am saving a JSON file to the storage on some button click. There are times when the file is an empty file(0 KB). So, most of the times it work as expected but this 0 KB file created a headache. There is no exception at all.
Thanks in advance!
BufferedWriter bw = null;
try {
File file = new File(path);
if (!file.exists()) {
file.createNewFile();
}
bw = new BufferedWriter(new FileWriter(file, false));
bw.write(content);
} catch (Exception e) {
Logger.e(mContext,"Write To File",e.toString());
}
finally {
try {
if (bw != null) {
bw.close();
}
}catch (Exception e)
{
Logger.e(mContext,"Write To File",e.toString());
}
}

I had the same issue. Solved it that way:
fw = new FileWriter(file, false);
bw = new BufferedWriter(fw);
...
bw.flush();
bw.close();
fw.close();

Create multiple files

I have this code:
try {
File file = new File(something+counter+".txt");
counter++;
if (!file.exists()) {
file.createNewFile();
}
FileWriter fw = new FileWriter(file.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write(content);
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
I need to make it like this: When they press enter, new file will be created in defined location (I made JTextField for this), but when they press it again, the file OVERWRITES. That's the problem. I need them to press enter - create new file: sample1.txt, press enter again, create new file: sample2.txt

OK by looking at your code now, it looks fine, but you probably declared the counter variable within the method. If so, it will be 'reset' to whatever you set it to every time the method is called.
EDIT:
This should work.
import java.io.*;
public class Example {
public static void main(String args[]) {
Example ex = new Example();
ex.writeFile();
ex.writeFile();
}
private void writeFile() {
try {
File file = new File("file" + counter + ".txt");
counter++;
System.out.println("Writing to " + file.toString());
if (!file.exists()) {
file.createNewFile();
}
FileWriter fw = new FileWriter(file.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write("content");
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private int counter = 0;
}
I get
Writing to file0.txt
Writing to file1.txt
as output and both files have the string 'content' written in them.
EDIT2:
Call writefile whenever the user presses enter.

Java WriteFile can't see contents

I want to create a simple text file with some text in it.
import java.io.*;
class TextFileWriter{
public static void writeTextFile(String fileName, String s) {
FileWriter output = null;
try {
output = new FileWriter(fileName);
BufferedWriter writer = new BufferedWriter(output);
writer.write(s);
} catch (Exception e) {
throw new RuntimeException(e);
} finally {
if (output != null) {
try {
output.close();
} catch (IOException e) {
}
}
}
}
public static void main(String args[]){
writeTextFile("myText.txt","some text");
}
}
When i run this code i successfully create the text file but when i open it i don't see the contents ("some text"). What am I doing wrong?

You're closing underlying FileWriter but actual data are still stored (buffered) in BufferedWriter object. That's the object you have to close:
FileWriter output = new FileWriter(fileName);
BufferedWriter writer = new BufferedWriter(output);
writer.write(s);
writer.flush(); // Good practice but not required
writer.close();

Writing to multiple files without duplicating code Java

I have this code to write to a file when I add a user to an array list. The code works fine:
public void writeToFile(String content)
{
try {
File file = new File("H:/JavaWorkspace/TradingPlatformProject/User_Report.txt");
if (!file.exists()) {
file.createNewFile();
}
FileWriter fw = new FileWriter(file.getAbsoluteFile(), true);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(content + "\n" );
bw.close();
logger.info("Recorded to User Activity file");
} catch (IOException e) {
e.printStackTrace();
}
}
I want to write to a separate file when a user does something differently (say, request a permission upgrade). Is there any way I can write to a new file "UserRequests.txt" without duplicating this code?

Why not make the method more general?
public void writeToFile(String content, String fileName, String path)
{
try {
File file = new File(path + fileName);
if (!file.exists()) {
file.createNewFile();
}
FileWriter fw = new FileWriter(file.getAbsoluteFile(), true);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(content + "\n" );
bw.close();
logger.info("Recorded to User Activity file");
} catch (IOException e) {
e.printStackTrace();
}
}
Then you could use the method for writing all kinds of files :3

You should probably just use a 2nd argument, as in the following.
Moreover, you should close your Writers in a finally block. That way, you would be sure that the Writers are closed even if a exception occurred while writing.
public void writeToFile(String content, String path)
{
FileWriter fw
BufferedWriter bw
try {
File file = new File(path);
if (!file.exists()) {
file.createNewFile();
}
fw = new FileWriter(file.getAbsoluteFile(), true);
bw = new BufferedWriter(fw);
bw.write(content + "\n" );
bw.close();
logger.info("Recorded to User Activity file");
} catch (IOException e) {
e.printStackTrace();
} finally {
bw.close();
fw.close();
}
}

I would just pass in the file you want to write to:
public void writeToFile(String content, String filename){
And then:
File file = new File("H:/JavaWorkspace/TradingPlatformProject/"+filename);