Recursively create directory

Question

Does anyone know how to use Java to create sub-directories based on the alphabets (a-z) that is n levels deep?

 /a
    /a
        /a
        /b
        /c
        ..
    /b
        /a
        /b
        ..
    ..
        /a
        /b
        /c
        ..

/b
    /a
        /a
        /b
        ..
    /b
        /a
        /b
        ..
    ..
        /a
        /b
        ..
..
    /a
        /a
        /b
        ..
    /b
        /a
        /b
        ..
    ..
        /a
        /b
        ..

Solution 1

public static void main(String[] args) {
  File root = new File("C:\\SO");
  List<String> alphabet = new ArrayList<String>();
  for (int i = 0; i < 26; i++) {
    alphabet.add(String.valueOf((char)('a' + i)));
  }

  final int depth = 3;
  mkDirs(root, alphabet, depth);
}

public static void mkDirs(File root, List<String> dirs, int depth) {
  if (depth == 0) return;
  for (String s : dirs) {
    File subdir = new File(root, s);
    subdir.mkdir();
    mkDirs(subdir, dirs, depth - 1);
  }
}

mkDirs recusively creates a depth-level directory tree based on a given list of Strings, which, in the case of main, consists of a list of characters in the English alphabet.

Solution 2

You can simply use the mkdirs() method of java.io.File class.

Example:

new File("C:\\Directory1\\Directory2").mkdirs();

Solution 3

If you don't mind relying on a 3rd party API, the Apache Commons IO package does this directly for you. Take a look at FileUtils.ForceMkdir.

The Apache license is commercial software development friendly, i.e. it doesn't require you to distribute your source code the way the GPL does. (Which may be a good or a bad thing, depending on your point of view).

Solution 4

Since Java 7, java.nio is preferred

import java.nio.file.Files;
import java.nio.file.Paths;

...

Files.createDirectories(Paths.get("a/b/c"));

Solution 5

If you're using mkdirs() (as suggested by @Zhile Zou) and your File object is a file and not a directory, you can do the following:

// Create the directory structure
file.getParentFile().mkdirs();

// Create the file
file.createNewFile();

If you simply do file.mkdirs() it will create a folder with the name of the file.

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