Java File IO - List files and directories recursively

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:

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:

Related File IO Tutorials:

• Calculate total files, sub directories and size of a directory
• How to copy a directory programmatically in Java
• How to rename/move file or directory in Java

Other Java File IO Tutorials:

• How to Read and Write Text File in Java
• How to Read and Write Binary Files in Java
• Java IO - Common File and Directory Operations Examples
• Java Serialization Basic Example
• Understanding Java Externalization with Examples
• How to execute Operating System Commands in Java
• 3 ways for reading user's input from console in Java
• File change notification example with Watch Service API
• Java Scanner Tutorial and Code Examples
• How to compress files in ZIP format in Java
• How to extract ZIP file in Java

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.

Attachments:

ListDirectoryRecurisve.java

[sample program]

0.8 kB