Java SimpleFileVisitor Issue when encountering permission errors

Question

I am trying to search my hard drive for mp4 files and copy them into a specific folder. The problem is that I don't have permission to access folders like: "C:\Documents and Settings", so my program stops when it encounters those rather than continuing on.

I tried to create a blacklist but it don't work at all.

package S;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.attribute.BasicFileAttributes;

    public class C {
        public static void main(String args[]) throws IOException {
            Path dir = Paths.get("C:/");
        Files.walkFileTree(dir, new FindJavaVisitor());
    }

    private static class FindJavaVisitor extends SimpleFileVisitor<Path> {

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
            if (file.toString().contains(".mp4")) {
                file.toFile().renameTo(new File("C:/MP4/"+file.toFile().getName()));
            }
            return FileVisitResult.CONTINUE;
        }
    }
}

score 1 · Accepted Answer · edited May 11 '18 at 14:05

You have to override two methods.

The first is the visitFileFailed() method.

As the documentation states:

Unless overridden, this method re-throws the I/O exception that prevented the file from being visited.

You also have to override the postVisitDirectory() method; it has two arguments, the second being an IOException. If there is an error, the second argument will not be null and in this case, from the documentation again:

Unless overridden, this method returns CONTINUE if the directory iteration completes without an I/O exception; otherwise this method re-throws the I/O exception that caused the iteration of the directory to terminate prematurely.

Given your error, the second one is the one you want to override.

However, I see in your code that you do file.toFile().renameTo().

Do not use this. Use Files.move() instead.

Finally, you also move while you are iterating... this is not a very good idea. Recall that the list of files in a directory, for instance, and unlike with the old API, is dynamically populated!

You should create a "renaming" Map<Path, Path> and perform the renames after you have visited it all. At least that is how I would proceed in this case.

Java SimpleFileVisitor Issue when encountering permission errors

1 Answers1