Java File IO - List files and directories recursively

Details
Written by  
Last Updated on 29 July 2019   |   Print  Email


The article How to list files and directories in a directory explains very well about how to list all files and directories under a specific directory, however its examples are only for listing the first level files and directories (those which are directly under the parent directory). But a directory may contain many sub files and sub directories which are nested in many levels, as in the following screenshot, for example:

a directory

To list all sub files and sub directories nested in all levels, one solution is to use recursion algorithm:

  1. List files in the first level.
  2. For each file in the first level list files:
    1. If the file is a directory:
      • Print out directory name.
      • Repeat the step 1 and 2 with the current directory.
    2. If the file is a file:
      • Print out file name.
    3. Continue with next file.

The following method implements the above algorithm:

    public void listDirectory(String dirPath, int level) {
        File dir = new File(dirPath);
        File[] firstLevelFiles = dir.listFiles();
        if (firstLevelFiles != null && firstLevelFiles.length > 0) {
            for (File aFile : firstLevelFiles) {
                for (int i = 0; i < level; i++) {
                    System.out.print("\t");
                }
                if (aFile.isDirectory()) {
                    System.out.println("[" + aFile.getName() + "]");
                    listDirectory(aFile.getAbsolutePath(), level + 1);
                } else {
                    System.out.println(aFile.getName());
                }
            }
        }
    }

 

The listDirectory() method has two parameters:

    •           dirPath: Absolute path of the directory being listed.
    •           level: this number is used to indent the output, make the output looks like a hierarchical structure. The method must be invoked with the level = 0.

As you can see, inside the listDirectory() method, there is a call to itself:

 

listDirectory(aFile.getAbsolutePath(), level + 1);

 

That’s the point which makes the entire nested sub files and sub directories listed.

Here is a sample program:

import java.io.File;
/**
 *
 * @author www.codejava.net
 *
 */
public class ListDirectoryRecurisve {
    public void listDirectory(String dirPath, int level) {
        File dir = new File(dirPath);
        File[] firstLevelFiles = dir.listFiles();
        if (firstLevelFiles != null && firstLevelFiles.length > 0) {
            for (File aFile : firstLevelFiles) {
                for (int i = 0; i < level; i++) {
                    System.out.print("\t");
                }
                if (aFile.isDirectory()) {
                    System.out.println("[" + aFile.getName() + "]");
                    listDirectory(aFile.getAbsolutePath(), level + 1);
                } else {
                    System.out.println(aFile.getName());
                }
            }
        }
    }
    public static void main(String[] args) {
        ListDirectoryRecurisve test = new ListDirectoryRecurisve();
        String dirToList = System.getProperty("user.home") + File.separator + "Documents";
        test.listDirectory(dirToList, 0);
    }
}

 

The sample program lists all files and directories in the user’s Documents directory. The output looks like as the following screenshot:

output screenshot

 

Related File IO Tutorials:

 

Other Java File IO Tutorials: