Scala - Listing Files in a Directory

---

---

Scala is open to make use of any Java objects and java.io.File is one of the objects which can be used in Scala programming to read, write, delete files and directories, etc.

Listing Files in a Directory

You can list files in a directory using the list method of Java File class. This method returns an array of strings naming the files and directories in the directory denoted by the abstract pathname.

Example

Following is the example which shows you how to list the files in a directory named testDir −

import java.io._

object Demo {
   def main(args: Array[String]) = {
      val directory = new File("testDir")
      
      val files = directory.list()
      if (files != null) {
         println("Directory contents:")
         for (file <- files) {
            println(file)
         }
      } else {
         println("Failed to list directory contents")
      }
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

The above code will attempt to list the contents of the directory testDir. If the directory exists and its contents are listed successfully, it will print the names of the files and directories within it. If the listing fails for some reason, it will print "Failed to list directory contents".

This will produce the following result -

Directory contents:
file1.txt
file2.txt
subDir

Listing Files with a Specific Extension

You can list files with a specific extension using the listFiles method and a FilenameFilter.

Example

Following is the example which shows you how to list all .txt files in a directory named testDir −

import java.io._

object Demo {
   def main(args: Array[String]) = {
      val directory = new File("testDir")
      
      val txtFiles = directory.listFiles(new FilenameFilter {
         def accept(dir: File, name: String): Boolean = name.endsWith(".txt")
      })
      
      if (txtFiles != null) {
         println("Text files:")
         for (file <- txtFiles) {
            println(file.getName)
         }
      } else {
         println("Failed to list text files")
      }
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

The above code will attempt to list all .txt files in the directory testDir. If the directory exists and the files are listed successfully, it will print the names of the .txt files within it. If the listing fails for some reason, it will print "Failed to list text files".

This will produce the following result -

Text files:
file1.txt
file2.txt

Listing Files Recursively

You can list files in a directory and its subdirectories using recursion.

Example

Following is the example which shows you how to list all files in a directory named testDir and its subdirectories −

import java.io._

object Demo {
   def main(args: Array[String]) = {
      val directory = new File("testDir")
      
      println("Listing files recursively:")
      listFilesRecursively(directory)
   }
   
   def listFilesRecursively(directory: File): Unit = {
      val files = directory.listFiles()
      if (files != null) {
         for (file <- files) {
            if (file.isDirectory) {
               listFilesRecursively(file)
            } else {
               println(file.getPath)
            }
         }
      } else {
         println(s"Failed to list files for directory: ${directory.getPath}")
      }
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

The above code will attempt to list all files in the directory testDir and its subdirectories. If the directories exist and the files are listed successfully, it will print the paths of the files within them. If the listing fails for some reason, it will print "Failed to list files for directory: directoryPath".

This will produce the following result -

Listing files recursively:
testDir/file1.txt
testDir/file2.txt
testDir/subDir/file3.txt

Listing Hidden Files

You can list hidden files using the isHidden method of the File class.

Example

Following is the example which shows you how to list hidden files in a directory named testDir −

import java.io._

object Demo {
   def main(args: Array[String]) = {
      val directory = new File("testDir")
      
      val hiddenFiles = directory.listFiles(new FileFilter {
         def accept(file: File): Boolean = file.isHidden
      })
      
      if (hiddenFiles != null) {
         println("Hidden files:")
         for (file <- hiddenFiles) {
            println(file.getName)
         }
      } else {
         println("Failed to list hidden files")
      }
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

The above code will attempt to list hidden files in the directory testDir. If the directory exists and the files are listed successfully, it will print the names of the hidden files within it. If the listing fails for some reason, it will print "Failed to list hidden files".

This will produce the following result -

Hidden files:
.hiddenFile1
.hiddenFile2

Listing Files with Detailed Information

You can list files with detailed information, like file size and last modified date using the length and lastModified methods of the File class.

Example

Following is the example which shows you how to list files with detailed information in a directory named testDir −

import java.io._
import java.text.SimpleDateFormat

object Demo {
   def main(args: Array[String]) = {
      val directory = new File("testDir")
      val dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
      
      val files = directory.listFiles()
      if (files != null) {
         println("Files with detailed information:")
         for (file <- files) {
            val lastModified = dateFormat.format(file.lastModified())
            println(s"Name: ${file.getName}, Size: ${file.length()} bytes, Last Modified: $lastModified")
         }
      } else {
         println("Failed to list files")
      }
   }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

The above code will attempt to list files with detailed information in the directory testDir. If the directory exists and the files are listed successfully, it will print the names, sizes, and last modified dates of the files within it. If the listing fails for some reason, it will print "Failed to list files".

This will produce the following result -

Files with detailed information:
Name: file1.txt, Size: 1024 bytes, Last Modified: 2023-07-15 12:34:56
Name: file2.txt, Size: 2048 bytes, Last Modified: 2023-07-16 08:22:33

Handling Exceptions When Listing Files

When working with file operations, it is important to handle exceptions like SecurityException and IOException to make your code more robust.

Example

Following is the example which shows you how to handle exceptions when listing files −

import java.io.File

object Demo {
  def main(args: Array[String]): Unit = {
    try {
      val directory = new File("/restricted_directory")
      val files = directory.listFiles()
      
      if (files != null) {
        files.foreach(file => println(file.getName))
      } else {
        println("No files found or directory does not exist.")
      }
    } catch {
      case se: SecurityException => println(s"Permission denied: ${se.getMessage}")
      case ioe: java.io.IOException => println(s"I/O error occurred: ${ioe.getMessage}")
      case e: Exception => println(s"An unexpected error occurred: ${e.getMessage}")
    }
  }
}

Save the above program in Demo.scala. Use the following commands to compile and execute this program.

Command

> scalac Demo.scala
> scala Demo

Output

If an error occurs, the program will print an appropriate error message.

This will produce the following result -

Permission denied: [error message]