Delete directory recursively in Scala

Question

I am writing the following (with Scala 2.10 and Java 6):

import java.io._

def delete(file: File) {
  if (file.isDirectory) 
    Option(file.listFiles).map(_.toList).getOrElse(Nil).foreach(delete(_))
  file.delete
}

How would you improve it ? The code seems working but it ignores the return value of java.io.File.delete. Can it be done easier with scala.io instead of java.io ?

Solution 1

With pure scala + java way

import scala.reflect.io.Directory
import java.io.File

val directory = new Directory(new File("/sampleDirectory"))
directory.deleteRecursively()

deleteRecursively() Returns false on failure

Solution 2

Try this code that throws an exception if it fails:

def deleteRecursively(file: File): Unit = {
  if (file.isDirectory) {
    file.listFiles.foreach(deleteRecursively)
  }
  if (file.exists && !file.delete) {
    throw new Exception(s"Unable to delete ${file.getAbsolutePath}")
  }
}

You could also fold or map over the delete if you want to return a value for all the deletes.

Solution 3

Using scala IO

import scalax.file.Path

val path = Path.fromString("/tmp/testfile")    
try {
  path.deleteRecursively(continueOnFailure = false) 
} catch {
  case e: IOException => // some file could not be deleted
}

or better, you could use a Try

val path: Path = Path ("/tmp/file")
Try(path.deleteRecursively(continueOnFailure = false))

which will either result in a Success[Int] containing the number of files deleted, or a Failure[IOException].

Solution 4

From http://alvinalexander.com/blog/post/java/java-io-faq-how-delete-directory-tree

Using Apache Common IO

import org.apache.commons.io.FileUtils;
import org.apache.commons.io.filefilter.WildcardFileFilter;
public void deleteDirectory(String directoryName)
throws IOException
{
  try
  {
    FileUtils.deleteDirectory(new File(directoryName));
  }
  catch (IOException ioe)
  {
    // log the exception here
    ioe.printStackTrace();
    throw ioe;
  }
}

The Scala one can just do this...

import org.apache.commons.io.FileUtils
import org.apache.commons.io.filefilter.WildcardFileFilter
FileUtils.deleteDirectory(new File(outputFile))

Maven Repo Imports

Solution 5

Using the Java NIO.2 API:

import java.nio.file.{Files, Paths, Path, SimpleFileVisitor, FileVisitResult}
import java.nio.file.attribute.BasicFileAttributes

def remove(root: Path): Unit = {
  Files.walkFileTree(root, new SimpleFileVisitor[Path] {
    override def visitFile(file: Path, attrs: BasicFileAttributes): FileVisitResult = {
      Files.delete(file)
      FileVisitResult.CONTINUE
    }
    override def postVisitDirectory(dir: Path, exc: IOException): FileVisitResult = {
      Files.delete(dir)
      FileVisitResult.CONTINUE
    }
  })
}

remove(Paths.get("/tmp/testdir"))

Really, it's a pity that the NIO.2 API is with us for so many years and yet few people are using it, even though it is really superior to the old File API.

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