List all subdirectories present a directory in Java

This post will discuss how to list all subdirectories present a directory in Java.

1. Using `File#list()` method

The File#list() method is used to get the files and directories in a directory that satisfy the specified file name filter. You can override the accept() method of the FilenameFilter that returns true if the specified file should be included in the file list; false otherwise. To list all subdirectories, return true if and only if the file is a directory.

import java.io.File;

import java.io.FilenameFilter;

import java.util.Arrays;

public class Main {

public static void main(String[] args) {

String path = "/path/to/dir";

File file = new File(path);

String[] directories = file.list(new FilenameFilter() {

@Override

public boolean accept(File dir, String name) {

return new File(dir, name).isDirectory();

}

});

System.out.println(Arrays.toString(directories));

}

Download Code

The above code can be further shortened with Java 8 lambdas, as shown below:

import java.io.File;

import java.util.Arrays;

public class Main {

public static void main(String[] args) {

String path = "/path/to/dir";

File file = new File(path);

String[] directories = file.list((dir, name) -> new File(dir, name).isDirectory());

System.out.println(Arrays.toString(directories));

}

Download Code

2. Using `File#listFiles()` method

You can also use the File#listFiles() method to get a pathname list of the files and directories in the specified directory that satisfy the specified file filter. You can override the accept() method of the FileFilter that checks whether the supplied pathname should be included in the output.

import java.io.File;

import java.io.FileFilter;

import java.util.Arrays;

public class Main {

public static void main(String[] args) {

String path = "/path/to/dir";

File[] directories = new File(path).listFiles(new FileFilter() {

@Override

public boolean accept(File pathname) {

return pathname.isDirectory();

}

});

System.out.println(Arrays.toString(directories));

}

Download Code

The above code is equivalent to the following, which uses method reference:

import java.io.File;

import java.util.Arrays;

public class Main {

public static void main(String[] args) {

String path = "/path/to/dir";

File[] directories = new File(path).listFiles(File::isDirectory);

System.out.println(Arrays.toString(directories));

}

Download Code

3. Using `DirectoryStream`

Alternatively, you can use the DirectoryStream to iterate over the files in a directory that satisfy some condition. Here’s a simple example of its usage to filter only directories:

import java.io.IOException;

import java.nio.file.DirectoryStream;

import java.nio.file.FileSystems;

import java.nio.file.Files;

import java.nio.file.Path;

public class Main {

public static void main(String[] args) {

String path = "/path/to/dir";

try (DirectoryStream<Path> ds = Files.newDirectoryStream(

FileSystems.getDefault().getPath(path), Files::isDirectory)) {

for (Path p : ds) {

System.out.println(p.getFileName());

}

} catch (IOException e) {

e.printStackTrace();

}

Download Code

4. Using `Files.walk()` method

If you need to limit the maximum number of directory levels to visit, consider using the Files.walk() method that returns a Stream<Path>. It is available since JDK 1.8. To visit all levels, you can pass Integer.MAX_VALUE value.

import java.io.IOException;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.util.List;

import java.util.stream.Collectors;

public class Main {

public static void main(String[] args) throws IOException {

String path = "/path/to/dir";

List<Path> dirs = Files.walk(Paths.get(path), 1)

.filter(Files::isDirectory)

.collect(Collectors.toList());

System.out.println(dirs);

}

Download Code

That’s all about listing all subdirectories present a directory in Java.

List all subdirectories present a directory in Java

1. Using File#list() method

2. Using File#listFiles() method

3. Using DirectoryStream

4. Using Files.walk() method

Share this:

1. Using `File#list()` method

2. Using `File#listFiles()` method

3. Using `DirectoryStream`

4. Using `Files.walk()` method