Recursively create directory

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
   开发者_如何学Python     /b
        ..

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

Example:

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

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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).

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Since Java 7, java.nio is preferred

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

...

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

---

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.

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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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I would write a little utility method that takes the start and the end letter as well as the desired deepth as parameters. This method calls itself recursively till done:

 private static void createAlphabetFolders(File parent, int start, int end, int deepth){

    if(deepth <= 0){
      return;
    }

    for (int i=start; i < end; i++){

      // create the folder
      String folderName = "" + ((char) i);
      File folder = new File(parent, folderName);
      System.out.println("creating: " + folder.getPath());
      folder.mkdirs();

      // call recursively
      createAlphabetFolders(folder, start, end, deepth-1);
    }
  }

One would call it like this:

createAlphabetFolders(new File("abctest"), 'A', 'E', 5);

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Scala code:

  def makePathRecursive(path: String) = {
    import java.io.File
    import scala.util.{Try, Failure, Success}

    val pathObj = new File(path)
    pathObj.exists match {
      case true => // do nothing
      case false => Try(pathObj.mkdirs) match {
        case Success(_) => // it worked 
        case Failure(e) => // maybe created meanwhile by another thread
          pathObj.exists match { 
          case false => throw new Exception(e)
          case _ =>  
        }
      }
    }
  }

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You could use three loops over characters a-z like so:

import java.io.*;

public class FileCreate {

    public static void main(String[] args) throws Exception {
        char trunkDirectory = 'a';
        char branchDirectory = 'a';
        char leaf = 'a';

        while (trunkDirectory != '{') {
            while (branchDirectory != '{') {
                while (leaf != '{') {
                    System.out.println(trunkDirectory + "/" + branchDirectory + "/" + leaf++);
                }
                leaf = 'a';
                branchDirectory++;
            }
            branchDirectory = 'a';
            trunkDirectory++;
        }

    }
}

This simply outputs the paths to the console. You could use File#mkdirs() to create a recursive directory structure or create the directories in each intermediate part of the nested loop. I'll leave that for you to finish.

---

    // ensures parent directory is created
    File parentFile = destFile.getParentFile();
    if (parentFile != null && !parentFile.exists()) {
        parentFile.mkdirs();
    }

    // creates destination file
    if (!destFile.exists()) {
        destFile.createNewFile();
    }

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Apache commons addresses most of these. Try -

org.apache.commons.io.FileUtils.forceMkdir(directory);