List all subdirectories of a directory in Kotlin

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

1. Using `DirectoryStream`

A simple solution is to use DirectoryStream to iterate over the files in a directory that satisfies a predicate. To list all subdirectories, you can apply the filter using the File#isDirectory() function:

import java.io.IOException

import java.nio.file.FileSystems

import java.nio.file.Files

fun main() {

val path = "/path/to/dir"

try {

Files.newDirectoryStream(FileSystems.getDefault().getPath(path))

{ Files.isDirectory(it) }

.use { ds -> ds.forEach { println(it.fileName) }

}

} catch (e: IOException) {

e.printStackTrace()

}

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2. Using `Files.walk()` function

To limit the number of directory levels to visit, use the Files.walk() function. Its usage is demonstrated below, which limits the directory levels to 1. A value of Int.MAX_VALUE can be used to visit all levels.

import java.nio.file.Files

import java.nio.file.Paths

import kotlin.streams.toList

fun main() {

val path = "/path/to/dir"

val dirs = Files.walk(Paths.get(path), 1)

.filter { Files.isDirectory(it) }.toList()

println(dirs)

}

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3. Using `File` class

The File class provides the File#list() function to list all files and directories in a directory. The idea is to override the accept() function of the FilenameFilter interface to return true if the specified file is a directory and false otherwise.

import java.io.File

fun main() {

val path = "/path/to/dir"

val directories = File(path).list { dir, name -> File(dir, name).isDirectory}

println(directories?.contentToString())

}

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You can easily modify the code using the File#listFiles() and override the accept() function of the FileFilter interface to filter directories.

import java.io.File

fun main() {

val path = "/path/to/dir"

val directories = File(path).listFiles { pathname -> pathname.isDirectory }

println(directories!!.contentToString())

}

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That’s all about listing all subdirectories in a directory in Kotlin.

List all subdirectories of a directory in Kotlin

1. Using DirectoryStream

2. Using Files.walk() function

3. Using File class

Share this:

1. Using `DirectoryStream`

2. Using `Files.walk()` function

3. Using `File` class