I am using the NIO libraries but I am getting a strange error when I try to move files from one directory to another.
String yearNow = new SimpleDateFormat("yyyy").format(
Calendar.getInstance().getTime());
try {
DirectoryStream<Path> curYearStream =
Files.newDirectoryStream(sourceDir, "{" + yearNow + "*}");
//Glob for current year
Path newDir = Paths.get(sourceDir + "//" + yearNow);
if (!Files.exists(newDir) || !Files.isDirectory(newDir)) {
Files.createDirectory(newDir);
//create 2014 directory if it doesn't exist
}
}
Iterate over elements that start with "2014" and move them in the new directory (newDir, which is also called 2014)
for (Path p : curYearStream) {
System.out.println(p); //it prints out exactly the files that I need to move
Files.move(p, newDir); //java.nio.file.FileAlreadyExistsException
}
I get the java.nio.file.FileAlreadyExistsException because my folder (2014) already exists. What I actually want to do is move all the files that start with "2014" INSIDE the 2014 directory.
Better not going back to java.io.File and using NIO instead:
Path sourceDir = Paths.get("c:\\source");
Path destinationDir = Paths.get("c:\\dest");
try (DirectoryStream<Path> directoryStream = Files.newDirectoryStream(sourceDir)) {
for (Path path : directoryStream) {
System.out.println("copying " + path.toString());
Path d2 = destinationDir.resolve(path.getFileName());
System.out.println("destination File=" + d2);
Files.move(path, d2, REPLACE_EXISTING);
}
} catch (IOException ex) {
ex.printStackTrace();
}
Files.move is not equivalent to the mv command. It won't detect that the destination is a directory and move files into there.
You have to construct the full destination path, file by file. If you want to copy /src/a.txt to /dest/2014/, the destination path needs to be /dest/2014/a.txt.
You may want to do something like this:
File srcFile = new File("/src/a.txt");
File destDir = new File("/dest/2014");
Path src = srcFile.toPath();
Path dest = new File(destDir, srcFile.getName()).toPath(); // "/dest/2014/a.txt"
Continue with #Andrew's answer
If we use only Files.move(src, dst, StandardCopyOption.REPLACE_EXISTING); then it will delete source directory because we only provide a directory path not an absolute path of a particular file. So it will also delete a source directory when operation will be done.
Let's say source path is /opt/src which contains a csv files and destination path is /opt/dst and I want to move all files from src to dst and I'm using Files.move(src, dst, StandardCopyOption.REPLACE_EXISTING); this then it will move all the files to dst but it will delete a src directory after moving all files because we didn't provide an absolute path of a each file for src as well as dst. We should have to provide src path like /opt/src/foo.csv and dst path like /opt/dst/foo.csv then and then it will not delete a source directory.
DirectoryStream used to iterate over the entries in a directory. A directory stream allows for the convenient use of the for-each construct to iterate over a directory. So we get an absolute path for src and we use resolve method for resolving an absolute path for dst.
Please refer DirectoryStream for more information.
Try this code:
public class App
{
public void moveFromSourceToDestination(String sourceName,String destinationName)
{
File mydir = new File(sourceName);
if (mydir.isDirectory())
{
File[] myContent = mydir.listFiles();
for(int i = 0; i < myContent.length; i++)
{
File file1 = myContent[i];
file1.renameTo(new File(destinationName+file1.getName()));
}
}
}
public static void main(String [] args)
{
App app = new App();
String sourceName = "C:\\Users\\SourceFolder";
String destinationName = "C:\\Users\\DestinationFolder\\";
app.moveFromSourceToDestination(sourceName,destinationName);
}
}
Using java.io.File, its as simple as this:
File srcFile = new File(srcDir, fileName);
srcFile.renameTo(new File(destDir, "a.txt"));
It's the first time ever I tried to create a directory and following some links and directions from previous posts of other users I managed to cook up the following method.
But it doesn't work.The condition to trigger this method is 100% certainly triggered. So the error has to be in here. But I cant figure out what I did wrong since I am a first-timer with this.
public void makeDirectory(String path, String nameFolder) {
File dir = new File(path + "\nameFolder");
dir.mkdir();
}
Thank you for your time
EDIT: 'Doesn't work' means no directory is being created.
EDIT2:
Have been able to make it work thx to Niks Tyagi
public void makeDirectory(String path, String nameFolder) {
File dir = new File(path +"\\"+ nameFolder);
dir.mkdirs();
}
public void makeDirectory(String path, String nameFolder) {
File dir = new File(path + "\\nameFolder");
dir.mkdir(); // Use mkdirs() method for below reason
}
OR
public void makeDirectory(String path, String nameFolder) {
File dir = new File(path + File.separator+"nameFolder");
dir.mkdir(); // Use mkdirs() method for below reason
}
mkdirs() will create the specified directory path in its entirety where mkdir() will only create the bottom most directory.
I currently have the problem that I encounter an exception I never saw before and that's why I don't know how to handle it.
I want to create a file according to given parameters, but it won't work.
public static Path createFile(String destDir, String fileName) throws IOException {
FileAccess.createDirectory( destDir);
Path xpath = new Path( destDir + Path.SEPARATOR + fileName);
if (! xpath.toFile().exists()) {
xpath.toFile().createNewFile();
if(FileAccess.TRACE_FILE)Trace.println1("<<< createFile " + xpath.toString() );
}
return xpath;
}
public static void createDirectory(String destDir) {
Path dirpath = new Path(destDir);
if (! dirpath.toFile().exists()) {
dirpath.toFile().mkdir();
if(TRACE_FILE)Trace.println1("<<< mkdir " + dirpath.toString() );
}
}
Every time I run my application the following exception occurs:
java.io.IOException: The system cannot find the path specified
at java.io.WinNTFileSystem.createFileExclusively(Native Method)
at java.io.File.createNewFile(Unknown Source)
[...]
How do I get rid of it? (I am using Win7 64bit btw)
The problem is that a file can't be created unless the entire containing path already exists - its immediate parent directory and all parents above it.
If you have a path c:\Temp and no subdirectories below it, and you try to create a file called c:\Temp\SubDir\myfile.txt, that will fail because C:\Temp\SubDir doesn't exist.
Before
xpath.toFile().createNewFile();
add
xpath.toFile().mkdirs();
(I'm not sure if mkdirs() requires just the path in the object; if it does, then change that new line to
new File(destDir).mkdirs();
Otherwise, you'll get your filename created as a subdirectory instead! You can verify which is correct by checking your Windows Explorer to see what directories it created.)
// File (or directory) to be moved
File file = new File("filename");
// Destination directory
File dir = new File("directoryname");
// Move file to new directory
boolean success = file.renameTo(new File(dir, file.getName()));
if (!success) {
// File was not successfully moved
//can it be because file with file name already exists in destination?
}
If the file with name 'filename' already exists in the destination will it be replaced with a new one?
According to Javadoc:
Many aspects of the behavior of this method are inherently platform-dependent: The rename operation might not be able to move a file from one filesystem to another, it might not be atomic, and it might not succeed if a file with the destination abstract pathname already exists. The return value should always be checked to make sure that the rename operation was successful.
From Javadoc:
The rename operation might not be able
to move a file from one filesystem to
another, it might not be atomic, and
it might not succeed if a file with
the destination abstract pathname
already exists.
I tested the following code:
It works the first time, second time it fails as expected.
To move a file you should delete or rename the destination if required.
public class Test {
public static void main(String[] args) throws IOException {
File file = new File( "c:\\filename" );
file.createNewFile();
File dir = new File( "c:\\temp" );
boolean success = file.renameTo( new File( dir, file.getName() ) );
if ( !success ) {
System.err.println( "succ:" + success );
}
}
}
As it is system dependent you should not expect it to behave this or other way. Check it and implement your own logic.
Is there a standard and reliable way of creating a temporary directory inside a Java application? There's an entry in Java's issue database, which has a bit of code in the comments, but I wonder if there is a standard solution to be found in one of the usual libraries (Apache Commons etc.) ?
If you are using JDK 7 use the new Files.createTempDirectory class to create the temporary directory.
Path tempDirWithPrefix = Files.createTempDirectory(prefix);
Before JDK 7 this should do it:
public static File createTempDirectory()
throws IOException
{
final File temp;
temp = File.createTempFile("temp", Long.toString(System.nanoTime()));
if(!(temp.delete()))
{
throw new IOException("Could not delete temp file: " + temp.getAbsolutePath());
}
if(!(temp.mkdir()))
{
throw new IOException("Could not create temp directory: " + temp.getAbsolutePath());
}
return (temp);
}
You could make better exceptions (subclass IOException) if you want.
The Google Guava library has a ton of helpful utilities. One of note here is the Files class. It has a bunch of useful methods including:
File myTempDir = Files.createTempDir();
This does exactly what you asked for in one line. If you read the documentation here you'll see that the proposed adaptation of File.createTempFile("install", "dir") typically introduces security vulnerabilities.
If you need a temporary directory for testing and you are using jUnit, #Rule together with TemporaryFolder solves your problem:
#Rule
public TemporaryFolder folder = new TemporaryFolder();
From the documentation:
The TemporaryFolder Rule allows creation of files and folders that are guaranteed to be deleted when the test method finishes (whether it passes or fails)
Update:
If you are using JUnit Jupiter (version 5.1.1 or greater), you have the option to use JUnit Pioneer which is the JUnit 5 Extension Pack.
Copied from the project documentation:
For example, the following test registers the extension for a single test method, creates and writes a file to the temporary directory and checks its content.
#Test
#ExtendWith(TempDirectory.class)
void test(#TempDir Path tempDir) {
Path file = tempDir.resolve("test.txt");
writeFile(file);
assertExpectedFileContent(file);
}
More info in the JavaDoc and the JavaDoc of TempDirectory
Gradle:
dependencies {
testImplementation 'org.junit-pioneer:junit-pioneer:0.1.2'
}
Maven:
<dependency>
<groupId>org.junit-pioneer</groupId>
<artifactId>junit-pioneer</artifactId>
<version>0.1.2</version>
<scope>test</scope>
</dependency>
Update 2:
The #TempDir annotation was added to the JUnit Jupiter 5.4.0 release as an experimental feature. Example copied from the JUnit 5 User Guide:
#Test
void writeItemsToFile(#TempDir Path tempDir) throws IOException {
Path file = tempDir.resolve("test.txt");
new ListWriter(file).write("a", "b", "c");
assertEquals(singletonList("a,b,c"), Files.readAllLines(file));
}
Naively written code to solve this problem suffers from race conditions, including several of the answers here. Historically you could think carefully about race conditions and write it yourself, or you could use a third-party library like Google's Guava (as Spina's answer suggested.) Or you could write buggy code.
But as of JDK 7, there is good news! The Java standard library itself now provides a properly working (non-racy) solution to this problem. You want java.nio.file.Files#createTempDirectory(). From the documentation:
public static Path createTempDirectory(Path dir,
String prefix,
FileAttribute<?>... attrs)
throws IOException
Creates a new directory in the specified directory, using the given prefix to generate its name. The resulting Path is associated with the same FileSystem as the given directory.
The details as to how the name of the directory is constructed is implementation dependent and therefore not specified. Where possible the prefix is used to construct candidate names.
This effectively resolves the embarrassingly ancient bug report in the Sun bug tracker which asked for just such a function.
This is the source code to the Guava library's Files.createTempDir(). It's nowhere as complex as you might think:
public static File createTempDir() {
File baseDir = new File(System.getProperty("java.io.tmpdir"));
String baseName = System.currentTimeMillis() + "-";
for (int counter = 0; counter < TEMP_DIR_ATTEMPTS; counter++) {
File tempDir = new File(baseDir, baseName + counter);
if (tempDir.mkdir()) {
return tempDir;
}
}
throw new IllegalStateException("Failed to create directory within "
+ TEMP_DIR_ATTEMPTS + " attempts (tried "
+ baseName + "0 to " + baseName + (TEMP_DIR_ATTEMPTS - 1) + ')');
}
By default:
private static final int TEMP_DIR_ATTEMPTS = 10000;
See here
Do not use deleteOnExit() even if you explicitly delete it later.
Google 'deleteonexit is evil' for more info, but the gist of the problem is:
deleteOnExit() only deletes for normal JVM shutdowns, not crashes or killing the JVM process.
deleteOnExit() only deletes on JVM shutdown - not good for long running server processes because:
The most evil of all - deleteOnExit() consumes memory for each temp file entry. If your process is running for months, or creates a lot of temp files in a short time, you consume memory and never release it until the JVM shuts down.
As of Java 1.7 createTempDirectory(prefix, attrs) and createTempDirectory(dir, prefix, attrs) are included in java.nio.file.Files
Example:
File tempDir = Files.createTempDirectory("foobar").toFile();
This is what I decided to do for my own code:
/**
* Create a new temporary directory. Use something like
* {#link #recursiveDelete(File)} to clean this directory up since it isn't
* deleted automatically
* #return the new directory
* #throws IOException if there is an error creating the temporary directory
*/
public static File createTempDir() throws IOException
{
final File sysTempDir = new File(System.getProperty("java.io.tmpdir"));
File newTempDir;
final int maxAttempts = 9;
int attemptCount = 0;
do
{
attemptCount++;
if(attemptCount > maxAttempts)
{
throw new IOException(
"The highly improbable has occurred! Failed to " +
"create a unique temporary directory after " +
maxAttempts + " attempts.");
}
String dirName = UUID.randomUUID().toString();
newTempDir = new File(sysTempDir, dirName);
} while(newTempDir.exists());
if(newTempDir.mkdirs())
{
return newTempDir;
}
else
{
throw new IOException(
"Failed to create temp dir named " +
newTempDir.getAbsolutePath());
}
}
/**
* Recursively delete file or directory
* #param fileOrDir
* the file or dir to delete
* #return
* true iff all files are successfully deleted
*/
public static boolean recursiveDelete(File fileOrDir)
{
if(fileOrDir.isDirectory())
{
// recursively delete contents
for(File innerFile: fileOrDir.listFiles())
{
if(!FileUtilities.recursiveDelete(innerFile))
{
return false;
}
}
}
return fileOrDir.delete();
}
Well, "createTempFile" actually creates the file. So why not just delete it first, and then do the mkdir on it?
This code should work reasonably well:
public static File createTempDir() {
final String baseTempPath = System.getProperty("java.io.tmpdir");
Random rand = new Random();
int randomInt = 1 + rand.nextInt();
File tempDir = new File(baseTempPath + File.separator + "tempDir" + randomInt);
if (tempDir.exists() == false) {
tempDir.mkdir();
}
tempDir.deleteOnExit();
return tempDir;
}
As discussed in this RFE and its comments, you could call tempDir.delete() first. Or you could use System.getProperty("java.io.tmpdir") and create a directory there. Either way, you should remember to call tempDir.deleteOnExit(), or the file won't be deleted after you're done.
Just for completion, this is the code from google guava library. It is not my code, but I think it is valueable to show it here in this thread.
/** Maximum loop count when creating temp directories. */
private static final int TEMP_DIR_ATTEMPTS = 10000;
/**
* Atomically creates a new directory somewhere beneath the system's temporary directory (as
* defined by the {#code java.io.tmpdir} system property), and returns its name.
*
* <p>Use this method instead of {#link File#createTempFile(String, String)} when you wish to
* create a directory, not a regular file. A common pitfall is to call {#code createTempFile},
* delete the file and create a directory in its place, but this leads a race condition which can
* be exploited to create security vulnerabilities, especially when executable files are to be
* written into the directory.
*
* <p>This method assumes that the temporary volume is writable, has free inodes and free blocks,
* and that it will not be called thousands of times per second.
*
* #return the newly-created directory
* #throws IllegalStateException if the directory could not be created
*/
public static File createTempDir() {
File baseDir = new File(System.getProperty("java.io.tmpdir"));
String baseName = System.currentTimeMillis() + "-";
for (int counter = 0; counter < TEMP_DIR_ATTEMPTS; counter++) {
File tempDir = new File(baseDir, baseName + counter);
if (tempDir.mkdir()) {
return tempDir;
}
}
throw new IllegalStateException(
"Failed to create directory within "
+ TEMP_DIR_ATTEMPTS
+ " attempts (tried "
+ baseName
+ "0 to "
+ baseName
+ (TEMP_DIR_ATTEMPTS - 1)
+ ')');
}
I got the same problem so this is just another answer for those who are interested, and it's similar to one of the above:
public static final String tempDir = System.getProperty("java.io.tmpdir")+"tmp"+System.nanoTime();
static {
File f = new File(tempDir);
if(!f.exists())
f.mkdir();
}
And for my application, I decided that to add in a option to clear the temp on exit so I added in a shut-down hook:
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
//stackless deletion
String root = MainWindow.tempDir;
Stack<String> dirStack = new Stack<String>();
dirStack.push(root);
while(!dirStack.empty()) {
String dir = dirStack.pop();
File f = new File(dir);
if(f.listFiles().length==0)
f.delete();
else {
dirStack.push(dir);
for(File ff: f.listFiles()) {
if(ff.isFile())
ff.delete();
else if(ff.isDirectory())
dirStack.push(ff.getPath());
}
}
}
}
});
The method delete all subdirs and files before deleting the temp, without using the callstack (which is totally optional and you could do it with recursion at this point), but I want to be on the safe side.
As you can see in the other answers, no standard approach has arisen.
Hence you already mentioned Apache Commons, I propose the following approach using FileUtils from Apache Commons IO:
/**
* Creates a temporary subdirectory in the standard temporary directory.
* This will be automatically deleted upon exit.
*
* #param prefix
* the prefix used to create the directory, completed by a
* current timestamp. Use for instance your application's name
* #return the directory
*/
public static File createTempDirectory(String prefix) {
final File tmp = new File(FileUtils.getTempDirectory().getAbsolutePath()
+ "/" + prefix + System.currentTimeMillis());
tmp.mkdir();
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
try {
FileUtils.deleteDirectory(tmp);
} catch (IOException e) {
e.printStackTrace();
}
}
});
return tmp;
}
This is preferred since apache commons the library that comes as closest to the asked "standard" and works with both JDK 7 and older versions. This also returns an "old" File instance (which is stream based) and not a "new" Path instance (which is buffer based and would be the result of JDK7's getTemporaryDirectory() method) -> Therefore it returns what most people need when they want to create a temporary directory.
Try this small example:
Code:
try {
Path tmpDir = Files.createTempDirectory("tmpDir");
System.out.println(tmpDir.toString());
Files.delete(tmpDir);
} catch (IOException e) {
e.printStackTrace();
}
Imports:
java.io.IOException
java.nio.file.Files
java.nio.file.Path
Console output on Windows machine:
C:\Users\userName\AppData\Local\Temp\tmpDir2908538301081367877
Comment:
Files.createTempDirectory generates unique ID atomatically - 2908538301081367877.
Note:
Read the following for deleting directories recursively:
Delete directories recursively in Java
I like the multiple attempts at creating a unique name but even this solution does not rule out a race condition. Another process can slip in after the test for exists() and the if(newTempDir.mkdirs()) method invocation. I have no idea how to completely make this safe without resorting to native code, which I presume is what's buried inside File.createTempFile().
Before Java 7 you could also:
File folder = File.createTempFile("testFileUtils", ""); // no suffix
folder.delete();
folder.mkdirs();
folder.deleteOnExit();
Using File#createTempFile and delete to create a unique name for the directory seems ok. You should add a ShutdownHook to delete the directory (recursively) on JVM shutdown.