Java how to convert List of File objects to List of Path objects?

Question

I am building a library for which the user already has code that processes an array of Paths. I have this:

Collection<File> filesT = FileUtils.listFiles(
            new File(dir), new RegexFileFilter(".txt$"), 
            DirectoryFileFilter.DIRECTORY
          );

I use the List of File object throughout but needed a way to convert filesT to List<Path>. Is there a quick way, maybe lambda to quickly convert one list to the other?

And how did you mean to create a Path object from a File object? — Joakim Danielson, Oct 13 '20 at 20:14
To be clear, is the conversion from `java.io.File` to `java.nio.file.Path`? — John Kugelman, Oct 13 '20 at 20:16
Possibly related: [Get java.nio.file.Path object from java.io.File](https://stackoverflow.com/q/15512200) — Pshemo, Oct 13 '20 at 20:16
Why don’t you use `Path` in the first place? Getting a filtered list, including pattern matching, is already provided by the API. — Holger, Oct 14 '20 at 11:22

Nowhere Man · Accepted Answer · 2020-10-14T12:57:48.780

2

If you have a Collection<File>, you can convert it to List<Path> or to Path[] using File::toPath method reference:

public List<Path> filesToPathList(Collection<File> files) {
    return files.stream().map(File::toPath).collect(Collectors.toList());
}

public Path[] filesToPathArray(Collection<File> files) {
    return files.stream().map(File::toPath).toArray(Path[]::new);
}

edited Oct 14 '20 at 12:57

answered Oct 13 '20 at 21:22

Nowhere Man

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Sorry late response but this is how I did what I needed to do. I actually used Jim Newpower's Set type from above. So technically you both have the answer. Thank guys. – Mike Oct 28 '20 at 12:38

score 2 · Answer 2 · answered Oct 13 '20 at 22:01

I agree with Alex Rudenko's answer, however the toArray() would require a cast. I present an alternative (how I would implement, returning immutable collections):

Set<Path> mapFilesToPaths(Collection<File> files) {
    return files.stream().map(File::toPath).collect(Collectors.toUnmodifiableSet());
}

Java how to convert List of File objects to List of Path objects?

2 Answers2