Java - File listRoots()method

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Description

The Java File listRoots() method returns an array of File objects representing the available filesystem roots (drive letters on Windows or mount points on Linux/macOS). It helps list all the root directories present on the system.

Declaration

Following is the declaration for java.io.File.listRoots() method −

public static File[] listRoots()

Parameters

filter− File filter

Return Value

The method returns an array of File Objects indicating the available file system roots. The method returns null, if the set of roots could not be determined.

Exception

NA

Example - Usage of File listRoots() method

The following example shows the usage of Java File listRoots() method. We've created an array of files as File[] paths. Then we're getting all the roots in the current file system using File.listRoots() method call. As next step, we've iterated the result and print each path. In case of any exception during invocation of this method, we've handled the exception and printed the stack trace to figure out the root cause.

FileDemo.java

package com.tutorialspoint;

import java.io.File;

public class FileDemo {
   public static void main(String[] args) {      
      File[] paths;      
      try {  
      
         // returns pathnames for files and directory
         paths = File.listRoots();
         
         // for each pathname in pathname array
         for(File path:paths) {
         
            // prints file and directory paths
            System.out.println(path);
         }
         
      } catch(Exception e) {
         // if any error occurs
         e.printStackTrace();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result(depends on system's free space)−

C:\
F:\

Example - Listing All Root Directories

The following example shows the usage of Java File listRoots() method.

FileDemo.java

package com.tutorialspoint;

import java.io.File;

public class FileDemo {
   public static void main(String[] args) {
      // Get an array of filesystem roots
      File[] roots = File.listRoots();

      // Print each root directory
      System.out.println("Available filesystem roots:");
      for (File root : roots) {
         System.out.println(root.getAbsolutePath());
      }
   }
}

Output on Windows

Let us compile and run the above program, this will produce the following result−

Available filesystem roots:
C:\
D:\

Output on Linux\MacOS

Let us compile and run the above program, this will produce the following result−

Available filesystem roots:
/

Explanation

• The File.listRoots() method returns an array of root directories.

• The program loops through the array and prints each root directory.

Example - Listing Root Directories with Free Space Information

The following example shows the usage of Java File listRoots() method.

FileDemo.java

package com.tutorialspoint;

import java.io.File;

public class FileDemo {
   public static void main(String[] args) {
      // Get an array of filesystem roots
      File[] roots = File.listRoots();

      // Print each root directory along with free space
      System.out.println("Root directories and available space:");
      for (File root : roots) {
         long freeSpaceGB = root.getFreeSpace() / (1024 * 1024 * 1024);
         System.out.println(root.getAbsolutePath() + " - Free space: " + freeSpaceGB + " GB");
      }
   }
}

Output on Windows

Let us compile and run the above program, this will produce the following result (depends on system's free space)−

Root directories and available space:
C:\ - Free space: 150 GB
D:\ - Free space: 500 GB

Output on Linux/MacOS

Let us compile and run the above program, this will produce the following result (depends on system's free space) −

Root directories and available space:
/ - Free space: 200 GB

Explanation

• The File.listRoots() method gets all filesystem root directories.

• The program calculates and prints the free space for each root directory.

• On Windows, listRoots() returns drive letters like C:\, D:\, etc.

• On Linux/macOS, it usually returns / as the only root.