Java Program to Create Directories Recursively

A directory/folder is a File System used in computing that acts as a named memory location for storing related files or even subfolders. This allows better management of files and folders and is premised on the concept of real-world folders used for storing files. This system is the implementation of compartmentalization of the memory and makes the working space more organized. The Directory File System allows hierarchical arrangement as well as nesting of directories inside other directories.  

Recursion is the process through which a function calls itself. It is a very useful approach to break down complex problems into smaller subparts.

Approaches:

1. Using the mkdir() method
2. Using the createDirectory() method of the java.nio package

1. Using the mkdir() Method

The first approach is to import the java.io.File class and define a method named file() which internally makes use of the mkdir() function to recursively create directories. The algorithm used inside the file() method is described below.

Algorithm:

1. Create the file() method with the return type as void.
2. This method takes three parameters :
   • String md which stands for Main Directory.
   • String path which stands for the directory structure to be made where each character means a new directory
   • Int depth represents the number of directories to be made.
3. Declare the terminating condition as if (depth == 0) return.
4. Decrement the depth for each recursive call.
5. Check if the path string is 0 in length and display the message accordingly.
6. Append the md with the first character of the path string and remove the first character from the path string for each recursive call.
7. Create an object of the File class with md as a parameter.
8. Check if the directory already exists using the exists() method and display the message.
9. Else create the directory using the mkdir()method.
10. Make the recursive call.

Implementation: Below is the implementation of the above program.

// Java Program to Create Directories Recursively // Importing required classes import java.io.File; // Main class class GFG {  // Method  // To create directories  static void file(String md, String path, int depth)  {  // md stores the starting path each character in  // path represents new directory depth stores  // the number of directories to be created  // terminating condition  if (depth == 0)  return;  // Decrementing the depth by 1  depth -= 1;  // Checking if the path exists  if (path.length() == 0)  System.out.println("Path does not exist");  // execute if the path has more directories  else {  // appending the next directory  // would be md = md + "\\" +  // path.charAt(0) for windows  md = md + "/" + path.charAt(0);  // removing the first character  // from path string  path = path.substring(1);  // creating File object  File f = new File(md);  // if the directory already exists  if (f.exists()) {  System.out.println("The Directory "  + "already exists");  }  else {  // creating the directory  boolean val = f.mkdir();  if (val)  System.out.println(md + " created"  + " successfully");  else  System.out.println(  "Unable to "  + "create Directory");  }  }  // recursive call  file(md, path, depth);  }  // Driver method  public static void main(String[] args)  {  // creating class object  GFG ob = new GFG();  // path for windows -> "C:\\Users\\  // harshit\\Desktop"  ob.file("/home/mayur/Desktop", "abcd", 4);  } } 

Output:

Time complexity: O(n),The time complexity of the above program is O(n) as the program is iterating through the string characters one by one to create the directories.
Space complexity: O(1),The space complexity of the above program is O(1) as no extra space is required for execution.

2. Using the createDirectory() method of the java.nio package

This approach makes use of java.nio package to implement the code. We deploy the createDirectories() method here to create new directories. We also make use of the try-catch block to catch IO Errors. The Algorithm can be found below.

Algorithm:

1. Repeat steps through 1-6 as mentioned in the algorithm in approach 1.
2. Now, convert the string md to Path Instance using Path.gets() method.
3. Again, check if the Directory already exists using the exists() method.
4. If the Directory is not present, open a try-catch block, and create a new directory using createDirectories() method.
5. Else, display that the Directory already exists.
6. Make the recursive call

Below is the implementation of the above program.

// Java code to create directories recursively // importing the packages import java.nio.file.Paths; import java.nio.file.Path; import java.nio.file.Files; import java.io.IOException; class GFG {  // defining the recursive method  static void file(String md, String path, int depth)  {  // base case  if (depth == 0)  return;  // decrement the depth  depth -= 1;  // check if the path is empty  if (path.length() == 0)  System.out.println("Path does not exist");  else {  // appending the first character from  // path string  md = md + "/" + path.charAt(0);  // removing the first character from  // path string  path = path.substring(1);  // creating the path instance from  // path string  Path p = Paths.get(md);  // if the directory already exists  if (!Files.exists(p)) {  try {  // creating directory  Files.createDirectories(p);  System.out.println(md + " created"  + " successfully");  }  catch (IOException err) {  err.printStackTrace();  }  }  else  System.out.println("The directory "  + "already exists");  }  // recursive call  file(md, path, depth);  }  // Driver Code  public static void main(String[] args)  {  // creating the object of the class  GFG ob = new GFG();  // md would be -> "C:\\Users\\harshit\\  // Desktop for windows  ob.file("/home/mayur/Desktop", "klm", 5);  } } 

Output:

Time Complexity: O(N), where N is the number of characters in the path string.

Space Complexity: O(N) to store the path string in the recursive stack.