Can anyone please tell me how to delete a file in a directory after being opened and loaded on to a database?
Here is my code:
public static void main(String[] args) throws SQLException{
int Count= 0;
File directory = new File("C://Documents and Settings//welcome//My Documents//Bluetooth Exchange Folder");
directory.deleteOnExit();
File files[] = directory.listFiles();
for(int index = 0; index < files.length; index++){
try {
FileReader inp = new FileReader (files[index]);
BufferedReader buf = new BufferedReader(inp);
String strLine;
try {
while ((strLine = buf.readLine()) != null)
{
System.out.println(strLine);
String[] dbColumnValues = strLine.split("%");
Connect.DoInsertIntoDB(Long.parseLong(dbColumnValues[0]),dbColumnValues[1],dbColumnValues[2], dbColumnValues[3]);
Count++;
System.out.println(Count + " Row(s) are inserted into the Database");
GenHTML.gen();
}
}
But the files are not deleted in the directory.
Please can anyone correct the mistake in my code?
[Currently, I am testing with 3 files in the directory. After each file gets loaded to the datbase, I want each files to get deleted from the directory.]
Thanks in advance!
It is better to be explicit in your code.
File files[] = directory.listFiles();
for(int index = 0; index < files.length; index++){
{
// Process files[index]
// ...
boolean wasDeleted = files[index].delete();
if (!wasDeleted)
{
// Deal with error
}
}
Also, you need to close your file handles when you are done with them
FileReader inp = new FileReader (files[index]);
try
{
// ...
}
finally
{
inp.close();
}
The File.delete() and File.deleteOnExit() methods will only delete a directory if it's empty. You'll have to delete the files from the directory as you process them (and make sure there are no subdirectories). Alternatively you can use FileUtils.deleteDirectory() from Apache Commons IO at the end of your processing.
The double slashes seems suspect. Either use a single backslash, which you need to quote as \\, or use a single slash /.
Also, you could try using delete() when then method returns instead of deleteOnExit().
According to the API:
Requests that the file or directory denoted by this abstract pathname be deleted when the virtual machine terminates.
In your code, however, you are treating that function as if it immediately deletes the directory.
You can't delete a directory, unless it's empty. If the directory is not empty, it is necessary to first recursively delete all files and subdirectories in the directory.
So directory.deleteOnExit() won't work in your case.
More, I suggest you to explicitly delete the files, not using deleteOnExit(). It is a dumb function that won't delete the file on exit if all the input/output streams related to the file are not closed. Always close the streams and explicitly delete the files, then the directory.
Maybe what you need to do is to use the dispose() method for the component that opens the file. What could possibly be the situation is that the file is still seen as opened and locked by a component that it had been opened in, so you have to ensure you use the dispose() method to solve that problem.
Related
This is currently what I have to delete the file but it's not working. I thought it may be permission problems or something but it wasn't. The file that I am testing with is empty and exists, so not sure why it doesn't delete it.
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
file.delete();
Any help would be GREATLY appreciated!
I now have:
File file = new File(catName + ".txt");
String path = file.getCanonicalPath();
File filePath = new File(path);
filePath.delete();
To try and find the correct path at run time so that if the program is transferred to a different computer it will still find the file.
The problem could also be due to any output streams that you have forgotten to close. In my case I was working with the file before the file being deleted. However at one place in the file operations, I had forgotten to close an output stream that I used to write to the file that was attempted to delete later.
Be sure to find out your current working directory, and write your filepath relative to it.
This code:
File here = new File(".");
System.out.println(here.getAbsolutePath());
... will print out that directory.
Also, unrelated to your question, try to use File.separator to remain OS-independent. Backslashes work only on Windows.
I got the same problem! then realized that my directory was not empty. I found the solution in another thread: not able to delete the directory through Java
/**
* Force deletion of directory
* #param path
* #return
*/
static public boolean deleteDirectory(File path) {
if (path.exists()) {
File[] files = path.listFiles();
for (int i = 0; i < files.length; i++) {
if (files[i].isDirectory()) {
deleteDirectory(files[i]);
} else {
files[i].delete();
}
}
}
return (path.delete());
}
Try closing all the FileOutputStream/FileInputStream you've opened earlier in other methods ,then try deleting ,worked like a charm.
I suspect that the problem is that the path is incorrect. Try this:
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
if (file.exists()) {
file.delete();
} else {
System.err.println(
"I cannot find '" + file + "' ('" + file.getAbsolutePath() + "')");
}
If you want to delete file first close all the connections and streams.
after that delete the file.
In my case it was the close() that was not executing due to unhandled exception.
void method() throws Exception {
FileInputStream fis = new FileInputStream(fileName);
parse(fis);
fis.close();
}
Assume exception is being thrown on the parse(), which is not handled in this method and therefore the file is not closed, down the road, the file is being deleted, and that delete statement fails, and do not delete.
So, instead I had the code like this, then it worked...
try {
parse(fis);
}
catch (Exception ex) {
fis.close();
throw ex;
}
so basic Java, which sometimes we overlook.
As other answers indicate, on Windows you cannot delete a file that is open. However one other thing that can stop a file from being deleted on Windows is if it is is mmap'd to a MappedByteBuffer (or DirectByteBuffer) -- if so, the file cannot be deleted until the byte buffer is garbage collected. There is some relatively safe code for forcibly closing (cleaning) a DirectByteBuffer before it is garbage collected here: https://github.com/classgraph/classgraph/blob/master/src/main/java/nonapi/io/github/classgraph/utils/FileUtils.java#L606 After cleaning the ByteBuffer, you can delete the file. However, make sure you never use the ByteBuffer again after cleaning it, or the JVM will crash.
I want to create and delete some files located in /data/data/providers/downloads/cache. So far, I can download target files and save in /data/data/providers/downloads/cache successfully, but when I trying to delete a file located in /data/data/providers/downloads/cache it fails in the end. My methods are as follows
File directory = new File("/data/data/providers/downloads/cache");
File[] files = directory.listFiles();
I want to list all files, so that I can find the target files need to be deleted.
I found that listFiles() method always return NULL, so my question is, can I use listFile() to the dir /data/data/providers/downloads/cache ?
Any ideals are welcomed.
BR
Alan
I use this method: when i want to delete all the files including the directory.
static public boolean deleteDirectory(File path) {
if( path.exists() ) {
File[] files = path.listFiles();
if (files == null) {
return true;
}
for(int i = 0; i < files.length; i++) {
if(files[i].isDirectory()) {
deleteDirectory(files[i]);
}
else {
files[i].delete();
}
Log.d("Deleting Files", files[i].getPath());
}
}
return( path.delete() );
}
But android has it's own clear cache method you can use, but it requires you to actually save stuff to the cache. The problem might be that you never add anything to it, and you only have permission to clear your own cache?
How do I take advantage of Android's "Clear Cache" button Discusses the problem anyway :)
Good luck
EDIT:
Also, are you sure your file path is correct? You can use
Environment.getDownloadCacheDirectory()
in order to find the root directory to the cache i think?
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
I am very new at java and my be missing something very basic. When i run my code i am trying to add value to accounts created in the code. When i try to run the code i recieve an error that a file cannot be found, but i thought that the file was created inside the code.
import java.util.Scanner;
import java.io.File;
import java.io.IOException;
class DoPayroll
{
public static void main(String args[])
throws
IOException
{
Scanner diskScanner =
new Scanner(new File("EmployeeInfo.txt"));
for (int empNum = 1; empNum <= 3; empNum++)
{
payOneEmployee(diskScanner);
}
}
static void payOneEmployee(Scanner aScanner)
{
Employee anEmployee = new Employee();
anEmployee.setName(aScanner.nextLine());
anEmployee.setJobTitle(aScanner.nextLine());
anEmployee.cutCheck(aScanner.nextDouble());
aScanner.nextLine();
}
}
once run i recieve the following error
Exception in thread "main" java.io.FileNotFoundException: EmployeeInfo.txt (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:106)
at java.util.Scanner.<init>(Scanner.java:636)
at DoPayroll.main(jobexe.java:11)
i thought that in the above code using new Scanner(new File("EmployeeInfo.txt") would create the new file once i input a value. Please give me a simple solution and an explanation.
It will create a new file when you write to it. However to read from it, it must already exist. You might like to check it exists with
File file = new File("EmployeeInfo.txt");
if (file.exists()) {
Scanner diskScanner = new Scanner(file);
for (int empNum = 1; empNum <= 3; empNum++)
payOneEmployee(diskScanner);
}
The File object can't find the filename you've passed. You either need to pass the full path of EmployeeInfo.txt to new File(...) or make sure current working directory is the directory that contains this file.
The File constructor does not create a file. Rather, it creates the information in Java needed to access a file on disk. You'd have to actually do file IO in Java using the created File for a new file to be created.
The Scanner constructor requires an existing File. So you need a full path to the real, valid location of EmployeeInfo.txt or to create that file using File I/O first. This tutorial on I/O in Java will help.
You are mistaking instantiating an instance of class File with actually writing a temp file to Disk. Take this line
Scanner diskScanner =
new Scanner(new File("EmployeeInfo.txt"));
And replace it with this
File newFile = File.createTempFile("EmployeeInfo", ".txt");
Scanner diskScanner = new Scanner(newFile);
Edit: Peter makes a good point. I'm face palming right now.
You thought wrong :D A Scanner needs a existing file, which seems quite logical as it reads values and without a existing file its difficult to read. The documentation also states that:
Throws:
FileNotFoundException - if source is not found
So, in short: You must provide a readable, existing file to a scanner.
As the other answer explain, the file is not created just by using new File("EmployeeInfo.txt").
You can check is the file exists using
File file = new File("EmployeeInfo.txt");
if(file.exists()) {
//it exists
}
or you can create the file (if it doesn't exists yet) using
file.createNewFile();
that method returns true if the file was created and false if it already existed.
This is currently what I have to delete the file but it's not working. I thought it may be permission problems or something but it wasn't. The file that I am testing with is empty and exists, so not sure why it doesn't delete it.
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
file.delete();
Any help would be GREATLY appreciated!
I now have:
File file = new File(catName + ".txt");
String path = file.getCanonicalPath();
File filePath = new File(path);
filePath.delete();
To try and find the correct path at run time so that if the program is transferred to a different computer it will still find the file.
The problem could also be due to any output streams that you have forgotten to close. In my case I was working with the file before the file being deleted. However at one place in the file operations, I had forgotten to close an output stream that I used to write to the file that was attempted to delete later.
Be sure to find out your current working directory, and write your filepath relative to it.
This code:
File here = new File(".");
System.out.println(here.getAbsolutePath());
... will print out that directory.
Also, unrelated to your question, try to use File.separator to remain OS-independent. Backslashes work only on Windows.
I got the same problem! then realized that my directory was not empty. I found the solution in another thread: not able to delete the directory through Java
/**
* Force deletion of directory
* #param path
* #return
*/
static public boolean deleteDirectory(File path) {
if (path.exists()) {
File[] files = path.listFiles();
for (int i = 0; i < files.length; i++) {
if (files[i].isDirectory()) {
deleteDirectory(files[i]);
} else {
files[i].delete();
}
}
}
return (path.delete());
}
Try closing all the FileOutputStream/FileInputStream you've opened earlier in other methods ,then try deleting ,worked like a charm.
I suspect that the problem is that the path is incorrect. Try this:
UserInput.prompt("Enter name of file to delete");
String name = UserInput.readString();
File file = new File("\\Files\\" + name + ".txt");
if (file.exists()) {
file.delete();
} else {
System.err.println(
"I cannot find '" + file + "' ('" + file.getAbsolutePath() + "')");
}
If you want to delete file first close all the connections and streams.
after that delete the file.
In my case it was the close() that was not executing due to unhandled exception.
void method() throws Exception {
FileInputStream fis = new FileInputStream(fileName);
parse(fis);
fis.close();
}
Assume exception is being thrown on the parse(), which is not handled in this method and therefore the file is not closed, down the road, the file is being deleted, and that delete statement fails, and do not delete.
So, instead I had the code like this, then it worked...
try {
parse(fis);
}
catch (Exception ex) {
fis.close();
throw ex;
}
so basic Java, which sometimes we overlook.
As other answers indicate, on Windows you cannot delete a file that is open. However one other thing that can stop a file from being deleted on Windows is if it is is mmap'd to a MappedByteBuffer (or DirectByteBuffer) -- if so, the file cannot be deleted until the byte buffer is garbage collected. There is some relatively safe code for forcibly closing (cleaning) a DirectByteBuffer before it is garbage collected here: https://github.com/classgraph/classgraph/blob/master/src/main/java/nonapi/io/github/classgraph/utils/FileUtils.java#L606 After cleaning the ByteBuffer, you can delete the file. However, make sure you never use the ByteBuffer again after cleaning it, or the JVM will crash.