I am trying to figure out why my inputFile.delete() will not delete the file. After looking at numerous topics it looks like something is still using the file and hence it won't delete. But I can't figure it out. What am I missing??
File inputFile = new File("data/Accounts.txt");
File tempFile = new File("data/tmp.txt");
try {
tempFile.createNewFile();
BufferedReader reader = new BufferedReader(new FileReader(inputFile));
BufferedWriter writer = new BufferedWriter(new FileWriter(tempFile));
String line;
int i = 0;
for (User u : data) {
String toRemove = getIDByUsername(username);
while ((line = reader.readLine()) != null) {
if (line.contains(toRemove + " ")) {
line = (i + " " + username + " " + getStatusByUsername(username) + " " + password);
}
writer.write(line + "\n");
i++;
}
}
reader.close();
writer.close();
} catch (FileNotFoundException e) {
ex.FileNotFound();
} catch (IOException ee) {
ex.IOException();
} finally {
inputFile.delete();
tempFile.renameTo(inputFile);
}
You can have that much shorter and easier by using java.nio:
public static void main(String[] args) {
// provide the path to your file, (might have to be an absolute path!)
Path filePath = Paths.get("data/Accounts.txt");
// lines go here, initialize it as empty list
List<String> lines = new ArrayList<>();
try {
// read all lines (alternatively, you can stream them by Files.lines(...)
lines = Files.readAllLines(filePath);
// do your logic here, this is just a very simple output of the content
System.out.println(String.join(" ", lines));
// delete the file
Files.delete(filePath);
} catch (FileNotFoundException fnfe) {
// handle the situation of a non existing file (wrong path or similar)
System.err.println("The file at " + filePath.toAbsolutePath().toString()
+ " could not be found." + System.lineSeparator()
+ fnfe.toString());
} catch (FileSystemException fse) {
// handle the situation of an inaccessible file
System.err.println("The file at " + filePath.toAbsolutePath().toString()
+ " could not be accessed:" + System.lineSeparator()
+ fse.toString());
} catch (IOException ioe) {
// catch unexpected IOExceptions that might be thrown
System.err.println("An unexpected IOException was thrown:" + System.lineSeparator()
+ ioe.toString());
}
}
This prints the content of the file and deletes it afterwards.
You will want to do something different instead of just printing the content, but that will be possible, too ;-) Try it...
I am trying to figure out why my inputFile.delete() will not delete the file.
That's because the old file API is crappy specifically in this way: It has no ability to tell you why something is not succeeding. All it can do, is return 'false', which it will.
See the other answer, by #deHaar which shows how to do this with the newer API. Aside from being cleaner code and the newer API giving you more options, the newer API also fixes this problem where various methods, such as File.delete(), cannot tell you the reason for why it cannot do what you ask.
There are many, many issues with your code, which is why I strongly suggest you go with deHaar's attempt. To wit:
You aren't properly closing your resources; if an exception happens, your file handlers will remain open.
Both reading and writing here is done with 'platform default encoding', whatever that might be. Basically, never use those FileReader and FileWriter constructors. Fortunately, the new API defaults to UTF_8 if you fail to specify an encoding, which is more sensible.
your exception handling is not great (you're throwing away any useful messages, whatever ex.FileNotFound() might be doing here) - and you still try to delete-and-replace even if exceptions occur, which then fail, as your file handles are still open.
The method should be called getIdByUsername
Your toRemove string is the same every time, or at least, the username variable does not appear to be updated as you loop through. If indeed it never updates, move that line out of your loop.
Related
I have used the following code to write elements from an arraylist into a file, to be retrieved later on using StringTokenizer. It works perfect for 3 other arraylists but somehow for this particular one, it throws an exception when reading with .nextToken() and further troubleshooting with .countTokens() shows that it only has 1 token in the file. The delimiters for both write and read are the same - "," as per the other arraylists as well.
I'm puzzled why it doesnt work the way it should as with the other arrays when I have not changed the code structure.
=================Writing to file==================
public static void copy_TimeZonestoFile(ArrayList<AL_TimeZone> timezones, Context context){
try {
FileOutputStream fileOutputStream = context.openFileOutput("TimeZones.dat",Context.MODE_PRIVATE);
OutputStreamWriter writerFile = new OutputStreamWriter(fileOutputStream);
int TZsize = timezones.size();
for (int i = 0; i < TZsize; i++) {
writerFile.write(
timezones.get(i).getRegion() + "," +
timezones.get(i).getOffset() + "\n"
);
}
writerFile.flush();
writerFile.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
==========Reading from file (nested in thread/runnable combo)===========
public void run() {
if (fileTimeZones.exists()){
System.out.println("Timezone file exists. Loading.. File size is : " + fileTimeZones.length());
try{
savedTimeZoneList.clear();
BufferedReader reader = new BufferedReader(new InputStreamReader(openFileInput("TimeZones.dat")));
String lineFromTZfile = reader.readLine();
while (lineFromTZfile != null ){
StringTokenizer token = new StringTokenizer(lineFromTZfile,",");
AL_TimeZone timeZone = new AL_TimeZone(token.nextToken(),
token.nextToken());
savedTimeZoneList.add(timeZone);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e){
e.printStackTrace();
}
}
}
===================Trace======================
I/System.out: Timezone file exists. Loading.. File size is : 12373
W/System.err: java.util.NoSuchElementException
at java.util.StringTokenizer.nextToken(StringTokenizer.java:349)
at com.cryptotrac.trackerService$1R_loadTimeZones.run(trackerService.java:215)
W/System.err: at java.lang.Thread.run(Thread.java:764)
It appears that this line of your code is causing the java.util.NoSuchElementException to be thrown.
AL_TimeZone timeZone = new AL_TimeZone(token.nextToken(), token.nextToken());
That probably means that at least one of the lines in file TimeZones.dat does not contain precisely two strings separated by a single comma.
This can be easily checked by making sure that the line that you read from the file is a valid line before you try to parse it.
Using method split, of class java.lang.String, is preferable to using StringTokenizer. Indeed the javadoc of class StringTokenizer states the following.
StringTokenizer is a legacy class that is retained for compatibility reasons although its use is discouraged in new code. It is recommended that anyone seeking this functionality use the split method of String or the java.util.regex package instead.
Try the following.
String lineFromTZfile = reader.readLine();
while (lineFromTZfile != null ){
String[] tokens = lineFromTZfile.split(",");
if (tokens.length == 2) {
// valid line, proceed to handle it
}
else {
// optionally handle an invalid line - maybe write it to the app log
}
lineFromTZfile = reader.readLine(); // Read next line in file.
}
There are probably multiple things wrong, because I'd actually expect you to run into an infinite loop, because you are only reading the first line of the file and then repeatedly parse it.
You should check following things:
Make sure that you are writing the file correctly. What does the written file exactly contain? Are there new lines at the end of each line?
Make sure that the data written (in this case, "region" and "offset") never contain a comma, otherwise parsing will break. I expect that there is a very good chance that "region" contains a comma.
When reading files you always need to assume that the file (format) is broken. For example, assume that readLine will return an empty line or something that contains more or less than one comma.
I am writing a method that takes in a List of Twitter Status objects as a parameter, opens a log file containing String represenatations of Tweets, checks if any of the String representations of the Status objects are already written to the file - if so, it removes them from the list, if not it appends the Status to the file.
Everything is working up until I attempt to write to the file. Nothing is being written at all. I am led to believe that it is due to the method having the file open in two different places: new File("tweets.txt") and new FileWriter("tweets.txt, true).
Here is my method:
private List<Status> removeDuplicates(List<Status> mentions) {
File mentionsFile = new File("tweets.txt");
try {
mentionsFile.createNewFile();
} catch (IOException e1) {
// Print error + stacktrace
}
List<String> fileLines = new ArrayList<>();
try {
Scanner scanner = new Scanner(mentionsFile);
while (scanner.hasNextLine()) {
fileLines.add(scanner.nextLine());
}
scanner.close();
} catch (FileNotFoundException e) {
// Print error + stacktrace
}
List<Status> duplicates = new ArrayList<>();
for (Status mention : mentions) {
String mentionString = "#" + mention.getUser().getScreenName() + " \"" + mention.getText() + "\" (" + mention.getCreatedAt() + "\")";
if (fileLines.contains(mentionString)) {
duplicates.add(mention);
} else {
try {
Writer writer = new BufferedWriter(new FileWriter("tweets.txt", true));
writer.write(mentionString);
} catch (IOException e) {
// Print error + stacktrace
}
}
}
mentions.removeAll(duplicates);
return mentions;
}
I wrote here few thoughts looking your code.
Remember to always close the object Reader and Writer.
Have a look at try-with-resources statement :
try (Writer writer = new BufferedWriter(new FileWriter("tweets.txt", true))) {
writer.write(mentionString);
} catch (IOException e) {
// Print error + stacktrace
}
To read an entire file in a List<String>:
List<String> lines = Files.readAllLines(Paths.get("tweets.txt"), StandardCharsets.UTF_8);
And again, I think it's a bad practice write in the same file you're reading of.
I would suggest to write in a different file if you don't have a particular constraint.
But if you really want have this behavior there are few alternative.
Create a temporary file as output and, when you process is successfully completed, than move it to the old one using Files.move(from, to).
Edit: I just found out that not a IOExcpetion but a FilerException is thrown. Therefore I changed that in the description and the title.
I'm working with Annotation Processing to generate some files for my java project. Now I always get an FilerException when the Annotation Processing tries to generate my files.
This is the way I create the files (GenClass and GenAnnotation are custom classes that abstract the generated classes. They weren't changed in about half a year so I'm sure the error isn't somewhere there. The way I write the files also didn't change in the last year.):
public static boolean generateJavaSourceFile(final ProcessingEnvironment processingEnv,
final GenClass element, final String fileName, final Class<?> generatorClass) {
boolean succeed = false;
Writer fw = null;
Filer f = processingEnv.getFiler();
// Mark the class as generated
GenAnnotation generatedAnnotation = getAnnotation(generatorClass);
element.pushImport(generatedAnnotation);
element.addAnnotation(generatedAnnotation);
try {
JavaFileObject jfo = f.createSourceFile(fileName, (Element[]) null);
// create new java source file
fw = jfo.openWriter();
// write the GenClass object into file
fw.write(element.toString());
succeed = true;
} catch (FilerException e) {
LOGGER.severe("Couldn't generate file (" + fileName + ")!");
processingEnv.getMessager().printMessage(Kind.ERROR,
"Could not create source file " + fileName
+ " because it already exists");
throw new RuntimeException(e.getMessage(), e);
} catch (IOException e) {
LOGGER.severe("Couldn't generate file (" + fileName + ")!");
throw new RuntimeException(e.getMessage(), e);
} finally {
if (fw != null) {
try {
fw.close(); // flush and close the stream
} catch (IOException e) {
LOGGER.severe("Couldn't close file [" + fileName + "]!");
}
}
}
LOGGER.fine(fileName + " written");
return succeed;
This is the message of the exception:
Source file already created: /path/to/the/file/to/create
I did change something on my processors, however the error only occurs for a certain type of files (Filters we use to filter data) and I didn't change anything on the processor that generates the filters. I added a new processor that works with a different annotation and those file are generated correctly.
Does anyone know what the cause of this error could be?
I had an error in another processor (that had nothing to do with the processor that generates the Filters) and that caused this error. Now that I fixed that error also this behavior stopped. I'm not really sure why this FilerException happened all the time, however it is gone now.
I have the following Java code which iterates through all the files in a directory and deletes them.
for(File file : tmpDir.listFiles())
{
file.delete();
}
It does however not delete all files. Some, usually 20-30, out of a couple of thousand, are left behind when I do this. Is it possible to fix this, or have I stumbled upon some Java voodoo that is best left alone?
It returns a boolean value, you should check that. From the JavaDoc:
Returns:
true if and only if the file or directory is successfully deleted; false otherwise
You should check the value of the return and take action.
If it returns false it may well be that you do not have permission to delete the file.
In that case you can check whether the file is writeable by the application and if not attempt to make it writeable - again this returns a boolean. If successful you can try deleting again.
You could use a utility method:
private void deleteFile(final File f) throws IOException {
if (f.delete()) {
return;
}
if (!f.canWrite() && !f.setWritable(true)) {
throw new IOException("No write permissions on file '" + f + "' and cannot set writeable.");
}
if (!f.delete()) {
throw new IOException("Failed to delete file '" + f + "' even after setting writeable; file may be locked.");
}
}
I would also take their advice in the JavaDoc:
Note that the Files class defines the delete method to throw an
IOException when a file cannot be deleted. This is useful for error
reporting and to diagnose why a file cannot be deleted.
Provided that you are using Java 7 that is. That method throws a number of exceptions that you can handle:
try {
Files.delete(path);
} catch (NoSuchFileException x) {
System.err.format("%s: no such" + " file or directory%n", path);
} catch (DirectoryNotEmptyException x) {
System.err.format("%s not empty%n", path);
} catch (IOException x) {
// File permission problems are caught here.
System.err.println(x);
}
Example taken from the Oracle tutorial page.
Forcing the garbage collector to run using System.gc(); made all the files deletable.
Make sure that you don't have any open stream like BufferedReader/Writer, FileReader/Writer etc. First close them, then you should be able to delete the file.
One more point, E.g. if you open a BufferedReader via another reader like FileReader, you must close both of the readers seperately.
So instead of this:
BufferedReader reader = new BufferedReader(new FileReader(new File(filePath)););
do this:
BufferedReader bufferedReader = null;
FileReader fileReader = null;
try{
fileReader = new FileReader(readFile);
bufferedReader = new BufferedReader(fileReader);
}catch{...}
...
try {
fileReader.close();
bufferedReader .close();
readFile.delete();
} catch (IOException e) {
e.printStackTrace();
}
I need some help please writing the output to a file and I can't get it to work. If I use the System.out.println it works. If I create the file stream and Buffered Writer in the actual method, it creates the file but doesn't write anything to it. I'm assuming it's because my method is recursive and creates a new file every time the method calls it self again. So I created another print method and used the string value key[i] as the string parameter and it does nothing.
Any help is appreciated, thank you.
public void print(String s)throws IOException
{
fstream = new FileWriter("out.txt", true);
out = new BufferedWriter(fstream);
try{
out.write("From print: " + s + " ");
out.close();
}catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}
}
public void generate() throws IOException
{
while (k<randomWordNum())
{
if (randomNum() <= sumOfFreq[0])
{
//System.out.println(getKey[0] + " ");
print(getKey[i]);
i++;
k++;
generate();
}
if (randomNum() >= sumOfFreq[i] && randomNum() <= sumOfFreq[i+1])
{
//System.out.println("From generate: " + getKey[i+1] + " ");
print(getKey[i+1]);
i++;
k++;
generate();
}
else
{
i++;
generate();
}
}//while
}//generate
You need to .close the file to make sure things get written
I think that constructor of FileWriter will overwrite the file. So you'll need to use a code line like this:
fstream = new FileWriter("out.txt", true); // true for appending
Also, always close a file before it goes out of scope, otherwise it might never get flushed or closed if you are unlucky...
And one more thing, assuming that is not some sort of debug/troubleshooting code, "never" catch Exception. If you do catch it, be sure to re-throw it asyou got it after logging or whatever you did with it. But, in general, always catch a more specific exception type.