Prerequisites: File class
Given a main directory/folder, list all the files from it, and if this directory has other nested sub-directories, list files from them. It is pretty easy to observe a simple recursion pattern in the above problem.
Algorithm :
- Create a File object for the main directory.
- Get an array of files for the main directory.
- If array[i] is a file:
- Print out the file name.
- If array[i] is a directory :
- Print out directory name.
- Get array of files for current sub-directory.
- Repeat the step 3 and 4 with current sub-directory.
- Repeat the step 3 and 4 with next array[i].
Example 1:
Java
// Java program to print all files// in a folder(and sub-folders)import java.io.File;public class GFG { static void RecursivePrint(File[] arr, int index, int level) { // terminate condition if (index == arr.length) return; // tabs for internal levels for (int i = 0; i < level; i++) System.out.print("\t"); // for files if (arr[index].isFile()) System.out.println(arr[index].getName()); // for sub-directories else if (arr[index].isDirectory()) { System.out.println("[" + arr[index].getName() + "]"); // recursion for sub-directories RecursivePrint(arr[index].listFiles(), 0, level + 1); } // recursion for main directory RecursivePrint(arr, ++index, level); } // Driver Method public static void main(String[] args) { // Provide full path for directory(change // accordingly) String maindirpath = "C:\\Users\\Gaurav Miglani\\Desktop\\Test"; // File object File maindir = new File(maindirpath); if (maindir.exists() && maindir.isDirectory()) { // array for files and sub-directories // of directory pointed by maindir File arr[] = maindir.listFiles(); System.out.println( "**********************************************"); System.out.println( "Files from main directory : " + maindir); System.out.println( "**********************************************"); // Calling recursive method RecursivePrint(arr, 0, 0); } }} |
Output:
**********************************************
Files from main directory : C:\Users\Gaurav Miglani\Desktop\Test
**********************************************
Cormen.pdf
Extra-Items.pdf
XYZ.pdf
[Docs]
A.docx
B.doc
C.docx
ABC.pdf
JKL.pdf
[sheets]
XXX.csv
YYY.csv
results.pdf
[Resumes]
[Before2016]
Resume2015.doc
Resume2016.doc
[Before2014]
Resume2014.doc
Resume2017.doc
Resume2017.pdf
QA.doc
Testing.pdf
Example 2: Below is another recursive program. Here we use recursion only for nested sub-directories. For main directory files, we use foreach loop.
Java
// Recursive Java program to print all files// in a folder(and sub-folders)import java.io.File;public class GFG { static void RecursivePrint(File[] arr, int level) { // for-each loop for main directory files for (File f : arr) { // tabs for internal levels for (int i = 0; i < level; i++) System.out.print("\t"); if (f.isFile()) System.out.println(f.getName()); else if (f.isDirectory()) { System.out.println("[" + f.getName() + "]"); // recursion for sub-directories RecursivePrint(f.listFiles(), level + 1); } } } // Driver Method public static void main(String[] args) { // Provide full path for directory(change // accordingly) String maindirpath = "C:\\Users\\Gaurav Miglani\\Desktop\\Test"; // File object File maindir = new File(maindirpath); if (maindir.exists() && maindir.isDirectory()) { // array for files and sub-directories // of directory pointed by maindir File arr[] = maindir.listFiles(); System.out.println( "**********************************************"); System.out.println( "Files from main directory : " + maindir); System.out.println( "**********************************************"); // Calling recursive method RecursivePrint(arr, 0); } }} |
Output:
**********************************************
Files from main directory : C:\Users\Gaurav Miglani\Desktop\Test
**********************************************
Cormen.pdf
Extra-Items.pdf
XYZ.pdf
[Docs]
A.docx
B.doc
C.docx
ABC.pdf
JKL.pdf
[sheets]
XXX.csv
YYY.csv
results.pdf
[Resumes]
[Before2016]
Resume2015.doc
Resume2016.doc
[Before2014]
Resume2014.doc
Resume2017.doc
Resume2017.pdf
QA.doc
Testing.pdf
Example 3 –
Below is another iterative program to get all file name using Stack DS
Java
// Iterative Program to get all file names in Directory and// SubDirectoryimport java.io.*;class GFG { public static void main(String[] args) { // provide complete path for directory(to be changed // accordingly) String mainDir = "c:\\GFG\\example"; // File object File file = new File(mainDir); Stack<File> s = new Stack<>(); s.push(file); // initially stack is not empty System.out.println("Content of Directory " + mainDir + " is"); while (!s.empty()) { File tmpF = s.pop(); // check if it is a file or not if (tmpF.isFile()) { // print file name can code here according // to our need System.out.println(tmpF.getName()); } else if (tmpF.isDirectory()) { // It's an directory hence list and push all // files in stack File[] f = tmpF.listFiles(); for (File fpp : f) { s.push(fpp); } } // else if ends here } // stack is not empty loop ends here } // main function ends here} |
Output:
Content of Directory c:\GFG\example is example.txt testTwo.java testTwo.class test.java test.class test.java eg1.java eg1.class test.java test.class Students.java Students.class
NOTE: The above code won’t compile on online IDE to compile and execute it download in your local system.
This article is contributed by Gaurav Miglani. If you like Lazyroar and would like to contribute, you can write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the Lazyroar main page and help other Geeks. Please write comments if you find anything incorrect or you want to share more information about the topic discussed above.
