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file input out append

I am trying to write some coordinates to a file and later read it in as a string. So I need to have them written to file attached...without space or a new line, but my code writes only the first coordinate, that is pos_Let, but does not write pos_Num at all, not even with a space or on a new line.
So how can I get the code to write to file pos_LetposNum like that? Obviously I mean their references ;) ..thanks in advance
protected void writeCoordtoFile () throws IOException
{
File file = new File("FermiPresentCoord.txt");
boolean yes = file.createNewFile() ;
//boolean yes = exists();
if (yes == true)
{
// create a FileWriter Object
FileWriter writer = new FileWriter(file, true);
// Writes the content to the file
writer.write("");
writer.flush();
writer.write(pos_Let);
writer.flush();
writer.write(pos_Num);
writer.close();
}
else
{
// creates the file
file.createNewFile();
// creates a FileWriter Object
FileWriter out = new FileWriter(file);
// Writes the content to the file
out.write(pos_Let);
out.flush();
out.write(pos_Num);
out.flush();
out.close();
}
}

Quoting the method createNewFile():
Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. The check for the existence of the file and the creation of the file if it does not exist are a single operation that is atomic with respect to all other filesystem activities that might affect the file.
Note: this method should not be used for file-locking, as the resulting protocol cannot be made to work reliably. The FileLock facility should be used instead.
Returns:
true if the named file does not exist and was successfully created; false if the named file already exists
in your case, you first create the file, and createNewFile() returns true, so you go to the if block, appending the line to the current file. Then, createNewFile() returns false, since, the file exists! So, you go to the else block, and create the file again from scratch...
So, basically, just inverse the if with else, and don't call createNewFile() twice... With the least possible changes (so that you do not get confused) here is my simple suggestion:
protected void writeCoordtoFile () throws IOException
{
File file = new File("FermiPresentCoord.txt");
boolean fileDoesNotExist = file.createNewFile() ;
//boolean fileDoesNotExist = file does **not** exist!
if (fileDoesNotExist)
{
// create a FileWriter Object
FileWriter writer = new FileWriter(file);
// Writes the content to the file
writer.write(pos_Let);
writer.write(pos_Num);
writer.close();
}
else
{
// creates a FileWriter Object
FileWriter out = new FileWriter(file,true);
// Writes the content to the file
out.write(""); //not sure why you need that...
out.write(pos_Let);
out.write(pos_Num);
out.close();
}
}

I can not find out why you are checking the existence of the output file. Because, when you are using FileWriter if the file specified in the path does not exist, it would create it and open a character output stream to it. Also if it exists in that path, only opens the output stream and it is ready to write into.
Try the following code and see whats happening when you run it more than one times:
float posLat = 156.23589965f;
float posLon = 12.987564f;
File file = new File("c:/FermiPresentCoord.txt");
FileWriter writer = new FileWriter(file, true);
writer.append(posLat+",");
writer.append(posLon+",");
writer.flush();
writer.close();
There is no need to invoke the file.createNewFile() and/or checking the for the existence of the file when you want to write into it.
The second argument for the FileWriter constructor is append flag. So every time you create an output stream to a file with FileWriter(file, true) constructor it automatically appends to the data of the file.
Good Luck.

Appending Byte[] to end of a binary file

I'm parsing a file. I'm creating a new output file and will have to add the 'byte[] data' to it. From there I will need to append many many other 'byte[] data's to the end of the file. I'm thinking I'll get the user to add a command line parameter for the output file name as I already have them providing the file name which we are parsing. That being said if the file name is not yet created in the system I feel I should generate one.
Now, I have no idea how to do this. My program is currently using DataInputStream to get and parse the file. Can I use DataOutputStream to append? If so I'm wondering how I would append to the file and not overwrite.

If so I'm wondering how I would append to the file and not overwrite.
That's easy - and you don't even need DataOutputStream. Just FileOutputStream is fine, using the constructor with an append parameter:
FileOutputStream output = new FileOutputStream("filename", true);
try {
output.write(data);
} finally {
output.close();
}
Or using Java 7's try-with-resources:
try (FileOutputStream output = new FileOutputStream("filename", true)) {
output.write(data);
}
If you do need DataOutputStream for some reason, you can just wrap a FileOutputStream opened in the same way.

Files.write(new Path('/path/to/file'), byteArray, StandardOpenOption.APPEND);
This is for byte append. Don't forget about Exception

File file =new File("your-file");
FileWriter fileWritter = new FileWriter(file.getName(),true);
BufferedWriter bufferWritter = new BufferedWriter(fileWritter);
bufferWritter.write(your-string);
bufferWritter.close();
Of coruse put this in try - catch block.

Write some text to a File - Exception

I want to write data to a text file. But, in my application, i will want to keep on writing items to the text file (Which means, the text that i want to write, should be appended to the file - and not create a new file every time)
My code, is as follows; But how could i append text the next time i am writing something to the file ?
1.) The problem with the code below is, the first time writes to the file, but when i am trying to write for the 2nd time i get the following exception;
java.io.IOException: Stream closed
2.) I want to be able to write to the same file untill the application is closed. Therefore, how can i close the Stream when the application is closed ?
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
public class WriteToFileExample {
public void writeToFile(String stuff) {
try {
File file = new File("../somefile.txt");
if (!file.exists()) {
file.createNewFile();
}
FileWriter fw = new FileWriter(file.getAbsoluteFile(),true);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(stuff);
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
UPDATE 1
private File file;
public WriteToFileExample(){
file = new File("../somefile.txt");
}
public void writeToFile(String stuff) {
try {
if (!file.exists()) {
file.createNewFile();
}
FileWriter fw = new FileWriter(file.getAbsoluteFile());
BufferedWriter bw = new BufferedWriter(fw);
bw.write(stuff);
bw.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
EXCEPTION
Exception in thread "main" java.lang.NullPointerException
at com.proj.example.Log.WriteToFile(WriteToFileExample.java:3)
Which points to if (!file.exists()) {.

FileWriter fw = new FileWriter(file.getAbsoluteFile(), true);
Use the true argument for the FileWriter constructor.

You should create your FileWriter using the contructor that takes an extra boolean argument, that indicates that you want to append.
FileWriter fw = new FileWriter(file.getAbsoluteFile(), true);

You never close the FileWriter in your code. And from the documentation for the class:
Whether or not a file is available or may be created depends upon the
underlying platform. Some platforms, in particular, allow a file to be
opened for writing by only one FileWriter (or other file-writing
object) at a time. In such situations the constructors in this class
will fail if the file involved is already open.
Close the file writer before exiting your method, its good practice anyway. And yes, definitely do open the writer in append mode, if you don't want the files contents to be blown away every time you call your method.

Checking the api, says that the FileWriter constructor takes a boolean to flag whether to append or not. That answer your question?

Instead of doing this:
FileWriter fw = new FileWriter(file.getAbsoluteFile());
do as follow:
FileWriter fw = new FileWriter(file.getAbsoluteFile(),true);
As to append on a existing file FileWriter needs an extra argument as true here
FileWriter
public FileWriter(File file, boolean append) throws IOException
Constructs a FileWriter object given a File object. If the second argument is true, then bytes will be
written to the end of the file rather than the beginning.
Parameters:
file - a File object to write to
append - if true, then bytes will be
written to the end of the file rather than the beginning
Throws:
IOException - if the file exists but is a directory rather than a
regular file, does not exist but cannot be created, or cannot be
opened for any other reason
Since:
1.4

could not delete file neither via java nor manually

I have the following situation, within a servlet a create a file and then have to delete it.
When executing the file, I figured out that the file is still in the server, so I tried to remove it manually, I can't, I get the following message :
this file is opened by another program : javaw.exe
Here is my code :
public class GenerateFile extends Action {
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) throws IOException {
System.out.println("ok");
String fileName = request.getParameter("fileName");
Integer nbrParam = Integer.parseInt(request.getParameter("nbrParam"));
String[] valueParam = new String[nbrParam+1];
for(int i =1;i<=nbrParam;i++)
{ System.out.println(request.getParameter("param"+i));
valueParam[i]=request.getParameter("param"+i);
}
FileInputStream in = new FileInputStream("C:\\Users\\free\\Desktop\\myworkspace\\gestionRH\\WebRoot\\fiches\\"+fileName+".doc");
POIFSFileSystem fs = new POIFSFileSystem(in);
HWPFDocument doc = new HWPFDocument(fs);
Range r = doc.getRange();
for(int i=1;i<=nbrParam;i++)
{ System.out.println("<param"+i+">");
System.out.println(valueParam[i]);
r.replaceText("<param"+i+">", valueParam[i]);
}
File file = new File("C:\\Users\\free\\Desktop\\myworkspace\\gestionRH\\WebRoot\\fiches\\temp");
File temp = File.createTempFile("monfile",".doc",file);
String tempName =temp.getName();
doc.write( new FileOutputStream(temp));
OutputStream out = response.getOutputStream();
response.setContentType("application/rtf");
response.setHeader("Content-Disposition","attachment; filename=Decision");
FileInputStream in1 = new FileInputStream(temp);
byte[] buffer = new byte[4096];
int length;
while ((length = in1.read(buffer)) > 0){
out.write(buffer, 0, length);
}
in1.close();
out.flush();
System.out.println("C:\\Users\\free\\Desktop\\myworkspace\\gestionRH\\WebRoot\\fiches\\temp\\"+tempName);
File f = new File("C:\\Users\\free\\Desktop\\myworkspace\\gestionRH\\WebRoot\\fiches\\temp\\"+tempName);
f.delete();
return null;
}
}

You should close all the file-reading object instances. Besides, if you can delete the file manually, you should close java and then delete it, javaw is the process that launches java outside the console.

The problem is you are creating a new FileOutputStream(tempName) to write on that file, but never closing that outputstream (or another outputstream linked to it).
Do this:
FileOutputStream fos = newFileOutputStream(tempName);
// use it
fos.close(); // CLOSE IT!!
// then you can delete the file
Simplify
Maybe you could do the work another way, without temp files...
by example: doc.write(new FileOutputStream(tempName)) could be replaced by:
doc.write(response.getOutputStream());
This way doc sends its bytes directly to where you need them, not to a temp file eliminating the need for it.
The idea behind input/output streams is composing them. Input/OutputStream are the abstract base classes. And there are a lot of implementations:
based on memory: ByteArrayInput/OutputStream
based on files: FileInputOutputStream
compressing/decompressing to another outputstream: GZipInputOutputStream
and so on
The beauty of it is applying decorator pattern to add functionality. By example:
new GZipOutputStream(new ByteArrayOutputStream());
// creates an outputstreams that compress data received and send it to the other stream
// the BAOS then writes the received bytes to memory
new GZipOutputStream(new FileOutputStream());
// it's the same but sending compressed bytes to a file.

Seems like, you are not closing the file(out), thus it remains with the thread of this action, which is restricting it to get deleted.
Hope it helps.

maybe you should try ProcMon to find out what process exactly holds the file opened

For IO features, I would to suggest to use some kind of jar already provided by community.
For example, common-io.x-x.jar, spring-core.jar
Eg, org.apache.commons.io.FileUtils;
FileUtils.copyDirectory(from, to);
FileUtils.deleteDirectory(childDir);
FileUtils.forceDelete(springConfigDir);
FileUtils.writeByteArrayToFile(file, data);
org.springframework.util.FileSystemUtils;
FileSystemUtils.copyRecursively(from, to);
FileSystemUtils.deleteRecursively(dir);
good luck!

Whenever you open a file handler, you should close it. In a Java application that you want to run for a long period of time, you are strongly recommended to close all unused file handlers soon after you finish working with them.
Examples of common file handlers are FileOutputStream and FileInputstream. Here is a good example of how you open and close the FileOutputStream
FileOutputStream fos = null;
try {
fos = new FileOutputStream(tempName);
// do something
} catch (IOException ex) {
// deal with exceptions
} finally {
// close if fos is not null
if (fos != null) {
fos.close();
}
}
You should never do this:
doc.write( new FileOutputStream(temp));
because you can never close the file handler if it has no refernce to it.

Close a file created with FileOutputStream, for a next delete

I am currently facing some problem with a FileOutputStream in my Java code.
Actually I am using a FileOutputStream for creating a file, but then once the file is created there is no way for deleting it. As far as I could understand, this may come from the fact that the FileOutputstream is not closed.
On below my summarized code :
outFile = new FileOutputStream(dir+"\\"+fileName);
outFile.write("Test");
outFile.flush();
outFile.close();
outFile = null;
System.gc();
Then there is no way to delete the file, even "by hand". When my program is launched, I can't delete it on windows by a simple del. I also tried to remove content of the folder dir and it didn't worked neither, using this code :
static public void delDir( String place )
{
File path = new File( place );
System.out.println(path.exists());//return true
if( path.exists() )
{
File[] f = path.listFiles();
for( int j = 0 ; j < f.length ; j++ )
{
if( f[ j ].isDirectory() )
{
deleteDirectory( path+"\\"+f[ j ] );
}
f[ j ].delete();
}
}
}
So my question is :
How to close this file for a next delete (or how to delete it properly if we can't close it)?

It is a bug in Java. Yes it it rarely but they exists ;) Could you add after outFile.close()
outFile = null;
System.gc();
And then try to delete it. There are more possiblity if this is not working. Let me know.
UPDATE
For me it works:
public class FileDeleteExample {
public static void main(String[] args) throws Exception {
File f = new File("test.txt");
FileOutputStream outFile = null;
try {
outFile = new FileOutputStream(f);
outFile.write("Test".getBytes());
} finally {
outFile.flush();
outFile.close();
outFile = null;
System.gc();
}
f.delete();
}
}
UPDATE
I tried it with the example Sumit Singh mentioned by deleting the lines outFile=null; System.gc; and this works as well for me. So there should'nt be a problem with the FileOutputStream. Could you try the little example above and say whether it works or not?
UPDATE
void closeQuietly(FileOutputStream out) {
try { out.flush(); out.close(); } catch(Exception e) {}
}
Now just call the method in the finally block!

I had the same problem, the delete() method returned false for my File.
In my case, somewhere in between creating the file, writing to its FileOutputStream and deleting the file, i was using a FileInputStream and forgot to call close() for it.
So, maybe somewhere in your code you attached another stream to this file, and left it open.
Before finding the real source of the problem, i used a simle hack to temporarily fix this:
FileOutputStream fos = new FileOutputStream(myFile);
fos.close();
myFile.delete();
Right before calling delete on my File, i created another FileOutputStream over it and then just called close().
This unlocks all previuous locks on this file and lets you call delete().
Still it is not a good practice to do this. You should find out who uses your file and solve it the right way.

Well, the way to close a file output and input streams is:
name.close()
and your deletion code looks fine. My recommendation would be to use FileIO instead of FileOutputStream, unless you're using FileOutputStream for a good reason. Can you delete the file once the program closes?

Better to use FileUtils.deleteDirectory from Apache Commons IO. Overcomes the Java delete bug, reduces amount of code used and most of all, it works.
Instead of calling
delDir(place);
just call
FileUtils.deleteDirectory(new File(place));
Update:
In your delDir method, you call:
deleteDirectory(new File(path + "\\" + f[j]));
but the result of
File[] f = path.listFiles();
will already include the path in the file, so you can just use:
deleteDirectory( f[j].getPath() );

Not really related but:
This solution of the closing of a file helped me with another problem. When run a programme from java 6 the new process was suspended until I closed my application (in java 7 it was ok).
The solution based on this answer helped:
String[] com = new String[]{javaRun, arg1, arg2, arg3, arg4};
Process proc = Runtime.getRuntime().exec(com, null, dir);
proc = null;
System.gc();
This works with java 6. Thanks for inspiration.

The problem may be in the first line:
outFile = new FileOutputStream(dir+"\"+fileName);
Not sure the new is required.
Don't believe the directory should be included in the path. AFAIK the directory for FileOutputStream is defined as the app internal directory.
HTH