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How to create a directory in Java?

How do I create Directory/folder?

Once I have tested System.getProperty("user.home");

I have to create a directory (directory name "new folder" ) if and only if new folder does not exist.

please review your selection of the correct answer. The solution proposed by JigarJoshi is misleading. It doesn't address the problem correctly (see my comment). The (simple) solution proposed by Bozho is much better.
mkdir is idempotent in java. The implementation will do the check if the directory exists for you, and only create it if it does not exist.

B
Bozho
new File("/path/directory").mkdirs();

Here "directory" is the name of the directory you want to create/exist.


Much better answer than the one selected as the correct one by the OP. Checking for existence of the directory before creating it should become a well-known anti-pattern.
what if the directory is already exists? It would do overwriting? or skip the process.
it is clear: Returns: true if and only if the directory was created, along with all necessary parent directories; false otherwise
It won't overwrite an existing directory. It will return false.
p
paradocslover

After ~7 year, I will update it to better approach which is suggested by Bozho.

File theDir = new File("/path/directory");
if (!theDir.exists()){
    theDir.mkdirs();
}

-1: That is actually a really bad technique to create a directory. The access to the FS is not reserved to a dedicated resource. Between if(!theDir.exists()) and theDir.mkdir() the status could have changed, as well as it could change in between not creating the directory (because of exists returning true) and needing it. The result of the method exists should never be used to decide wether to create a directory or not. Just call mkdir, no exception will be thrown if it already exists.
@mwhs I understand that it's better to not check for the directory but I don't understand your justification (second part). Can't the status change between calling mkdir and needing the directory as well? I assume you meant that some other process deletes the directory.
@Episodex Directories are shared resources. Just don't use the above solution, it is wrong for different reasons. Unclear how the PO could have thought this is the correct answer. If you want assertions about IO resources you need to use locks, not booleans.
@mhws I know this post is a couple months old but if you look at the mkdirs implementation, from the source code, the very first thing that gets called is if (exists()) { return false; }. The implementation itself checks first to see if the directory already exists so the only thing this answer is at fault for, perhaps, is checking that condition 2x. Not near as bad as you're making it out to be.
As of Java 7, you should probably use the methods in Files as in the more recent answer by Benoit Blanchon. (This answer appears to have been written before Java 7.)
B
Benoit Blanchon

With Java 7, you can use Files.createDirectories().

For instance:

Files.createDirectories(Paths.get("/path/to/directory"));

I think this option didn't exist at the time of the original Q&A, but this should be the answer going forward, I think.
It would also be good to note that: Unlike the createDirectory method, an exception is not thrown if the directory could not be created because it already exists
Thanks for pointing the difference btw createDirectory and createDirectories. I find it a poor naming choice.
(2019) I used Files.createDirectory(Paths.get(directory.toString())); where directory is a File object. Don't forget to catch your IOException
@chrips It is better to do directory.toPath() then.
S
Suzana

You can try FileUtils#forceMkdir

FileUtils.forceMkdir("/path/directory");

This library have a lot of useful functions.


Much better than pure mkdirs: handles concurrency, checks if the operation succeeded, checks if the directory (not a file!) exists.
Where does it say it handles concurrency? I actually tried to find it before I read this, looking for a way to let several threads manipulate filesystem without messing up.
Use the source Luke
B
Bruce

mkdir vs mkdirs

If you want to create a single directory use mkdir

new File("/path/directory").mkdir();

If you want to create a hierarchy of folder structure use mkdirs

 new File("/path/directory").mkdirs();

y
youpilat13

Create a single directory. new File("C:\\Directory1").mkdir(); Create a directory named “Directory2 and all its sub-directories “Sub2″ and “Sub-Sub2″ together. new File("C:\\Directory2\\Sub2\\Sub-Sub2").mkdirs()

Source: this perfect tutorial , you find also an example of use.


g
groo

For java 7 and up:

Path path = Paths.get("/your/path/string");
Files.createDirectories(path);

It seems unnecessary to check for existence of the dir or file before creating, from createDirectories javadocs:

Creates a directory by creating all nonexistent parent directories first. Unlike the createDirectory method, an exception is not thrown if the directory could not be created because it already exists. The attrs parameter is optional file-attributes to set atomically when creating the nonexistent directories. Each file attribute is identified by its name. If more than one attribute of the same name is included in the array then all but the last occurrence is ignored. If this method fails, then it may do so after creating some, but not all, of the parent directories.


J
Jon Freedman

The following method should do what you want, just make sure you are checking the return value of mkdir() / mkdirs()

private void createUserDir(final String dirName) throws IOException {
    final File homeDir = new File(System.getProperty("user.home"));
    final File dir = new File(homeDir, dirName);
    if (!dir.exists() && !dir.mkdirs()) {
        throw new IOException("Unable to create " + dir.getAbsolutePath();
    }
}

As mentioned in the comment by @mwhs on Jigar Joshi's answer, checking for existence first is not only not necessary but actually a bad idea.
R
Ripon Al Wasim

Neat and clean:

import java.io.File;

public class RevCreateDirectory {

    public void revCreateDirectory() {
        //To create single directory/folder
        File file = new File("D:\\Directory1");
        if (!file.exists()) {
            if (file.mkdir()) {
                System.out.println("Directory is created!");
            } else {
                System.out.println("Failed to create directory!");
            }
        }
        //To create multiple directories/folders
        File files = new File("D:\\Directory2\\Sub2\\Sub-Sub2");
        if (!files.exists()) {
            if (files.mkdirs()) {
                System.out.println("Multiple directories are created!");
            } else {
                System.out.println("Failed to create multiple directories!");
            }
        }

    }
}

b
bdean20

Though this question has been answered. I would like to put something extra, i.e. if there is a file exist with the directory name that you are trying to create than it should prompt an error. For future visitors.

public static void makeDir()
{
    File directory = new File(" dirname ");
    if (directory.exists() && directory.isFile())
    {
        System.out.println("The dir with name could not be" +
        " created as it is a normal file");
    }
    else
    {
        try
        {
            if (!directory.exists())
            {
                directory.mkdir();
            }
            String username = System.getProperty("user.name");
            String filename = " path/" + username + ".txt"; //extension if you need one

        }
        catch (IOException e)
        {
            System.out.println("prompt for error");
        }
    }
}

As mentioned in the comment by @mwhs on Jigar Joshi's answer, checking for existence first is not only not necessary but actually a bad idea.
M
Matt

Just wanted to point out to everyone calling File.mkdir() or File.mkdirs() to be careful the File object is a directory and not a file. For example if you call mkdirs() for the path /dir1/dir2/file.txt, it will create a folder with the name file.txt which is probably not what you wanted. If you are creating a new file and also want to automatically create parent folders you can do something like this:

            File file = new File(filePath);
            if (file.getParentFile() != null) {
                file.getParentFile().mkdirs();
            }

S
Stefano Castagnino

This the way work for me do one single directory or more or them: need to import java.io.File; /*enter the code below to add a diectory dir1 or check if exist dir1, if does not, so create it and same with dir2 and dir3 */

    File filed = new File("C:\\dir1");
    if(!filed.exists()){  if(filed.mkdir()){ System.out.println("directory is created"); }} else{ System.out.println("directory exist");  }

    File filel = new File("C:\\dir1\\dir2");
    if(!filel.exists()){  if(filel.mkdir()){ System.out.println("directory is created");   }} else{ System.out.println("directory exist");  }

    File filet = new File("C:\\dir1\\dir2\\dir3");
    if(!filet.exists()){  if(filet.mkdir()){ System.out.println("directory is  created"); }}  else{ System.out.println("directory exist");  }

V
Virb

if you want to be sure its created then this:

final String path = "target/logs/";
final File logsDir = new File(path);
final boolean logsDirCreated = logsDir.mkdir();
if (!logsDirCreated) {
    final boolean logsDirExists = logsDir.exists();
    assertThat(logsDirExists).isTrue();
}

beacuse mkDir() returns a boolean, and findbugs will cry for it if you dont use the variable. Also its not nice...

mkDir() returns only true if mkDir() creates it. If the dir exists, it returns false, so to verify the dir you created, only call exists() if mkDir() return false.

assertThat() will checks the result and fails if exists() returns false. ofc you can use other things to handle the uncreated directory.


B
Bouba

This function allows you to create a directory on the user home directory.

private static void createDirectory(final String directoryName) {
    final File homeDirectory = new File(System.getProperty("user.home"));
    final File newDirectory = new File(homeDirectory, directoryName);
    if(!newDirectory.exists()) {
        boolean result = newDirectory.mkdir();

        if(result) {
            System.out.println("The directory is created !");
        }
    } else {
        System.out.println("The directory already exist");
    }
}

As mentioned in the comment by @mwhs on Jigar Joshi's answer, checking for existence first is not only not necessary but actually a bad idea.
F
Fathah Rehman P
public class Test1 {
    public static void main(String[] args)
    {
       String path = System.getProperty("user.home");
       File dir=new File(path+"/new folder");
       if(dir.exists()){
           System.out.println("A folder with name 'new folder' is already exist in the path "+path);
       }else{
           dir.mkdir();
       }

    }
}

As mentioned in the comment by @mwhs on Jigar Joshi's answer, checking for existence first is not only not necessary but actually a bad idea.