How to create a temporary directory/folder in Java?

Peter_Becker_19820 0
Viewed 447673

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.) ?

temporary-directory file-io directory file java
18 Answers

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.

TofuBeer_658680

Well, "createTempFile" actually creates the file. So why not just delete it first, and then do the mkdir on it?

Paul_Tomblin_33330

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.

user_135310

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;
}
user_42490

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

user_64224590

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().

user_5732330

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.

ordnungswidrig_90690
Related