Recursively list files in Java

FileUtils have iterateFiles and listFiles methods. Give them a try. (from commons-io)

Edit: You can check here for a benchmark of different approaches. It seems that the commons-io approach is slow, so pick some of the faster ones from here (if it matters)

// Ready to run

import java.io.File;

public class Filewalker {

    public void walk( String path ) {

        File root = new File( path );
        File[] list = root.listFiles();

        if (list == null) return;

        for ( File f : list ) {
            if ( f.isDirectory() ) {
                walk( f.getAbsolutePath() );
                System.out.println( "Dir:" + f.getAbsoluteFile() );
            }
            else {
                System.out.println( "File:" + f.getAbsoluteFile() );
            }
        }
    }

    public static void main(String[] args) {
        Filewalker fw = new Filewalker();
        fw.walk("c:\\" );
    }

}

Java 7 will have has Files.walkFileTree:

If you provide a starting point and a file visitor, it will invoke various methods on the file visitor as it walks through the file in the file tree. We expect people to use this if they are developing a recursive copy, a recursive move, a recursive delete, or a recursive operation that sets permissions or performs another operation on each of the files.

There is now an entire Oracle tutorial on this question.

I would go with something like:

public void list(File file) {
    System.out.println(file.getName());
    File[] children = file.listFiles();
    for (File child : children) {
        list(child);
    }
}

The System.out.println is just there to indicate to do something with the file. there is no need to differentiate between files and directories, since a normal file will simply have zero children.

just write it yourself using simple recursion:

public List<File> addFiles(List<File> files, File dir)
{
    if (files == null)
        files = new LinkedList<File>();

    if (!dir.isDirectory())
    {
        files.add(dir);
        return files;
    }

    for (File file : dir.listFiles())
        addFiles(files, file);
    return files;
}

This code is ready to run

public static void main(String... args) {
    File[] files = new File("D:/").listFiles();
    if (files != null) 
       getFiles(files);
}

public static void getFiles(File[] files) {
    for (File file : files) {
        if (file.isDirectory()) {
            getFiles(file.listFiles());
        } else {
            System.out.println("File: " + file);
        }
    }
}

I think this should do the work:

File dir = new File(dirname);
String[] files = dir.list();

This way you have files and dirs. Now use recursion and do the same for dirs (File class has isDirectory() method).

Apart from the recursive traversal one can use a Visitor based approach as well.

Below code is uses Visitor based approach for the traversal.It is expected that the input to the program is the root directory to traverse.

public interface Visitor {
    void visit(DirElement d);
    void visit(FileElement f);
}

public abstract class Element {
    protected File rootPath;
    abstract void accept(Visitor v);

    @Override
    public String toString() {
        return rootPath.getAbsolutePath();
    }
}

public class FileElement extends Element {
    FileElement(final String path) {
        rootPath = new File(path);
    }

    @Override
    void accept(final Visitor v) {
        v.visit(this);
    }
}

public class DirElement extends Element implements Iterable<Element> {
    private final List<Element> elemList;
    DirElement(final String path) {
        elemList = new ArrayList<Element>();
        rootPath = new File(path);
        for (File f : rootPath.listFiles()) {
            if (f.isDirectory()) {
                elemList.add(new DirElement(f.getAbsolutePath()));
            } else if (f.isFile()) {
                elemList.add(new FileElement(f.getAbsolutePath()));
            }
        }
    }

    @Override
    void accept(final Visitor v) {
        v.visit(this);
    }

    public Iterator<Element> iterator() {
        return elemList.iterator();
    }
}

public class ElementWalker {
    private final String rootDir;
    ElementWalker(final String dir) {
        rootDir = dir;
    }

    private void traverse() {
        Element d = new DirElement(rootDir);
        d.accept(new Walker());
    }

    public static void main(final String[] args) {
        ElementWalker t = new ElementWalker("C:\\temp");
        t.traverse();
    }

    private class Walker implements Visitor {
        public void visit(final DirElement d) {
            System.out.println(d);
            for(Element e:d) {
                e.accept(this);
            }
        }

        public void visit(final FileElement f) {
            System.out.println(f);
        }
    }
}

I came up with this for printing all the files/file names recursively.

private static void printAllFiles(String filePath,File folder) {
    if(filePath==null) {
        return;
    }
    File[] files = folder.listFiles();
    for(File element : files) {
        if(element.isDirectory()) {
            printAllFiles(filePath,element);
        } else {
            System.out.println(" FileName "+ element.getName());
        }
    }
}

Lists all files with provided extensions,with option to scan subfolders (recursive)

 public static ArrayList<File> listFileTree(File dir,boolean recursive) {
        if (null == dir || !dir.isDirectory()) {
            return new ArrayList<>();
        }
        final Set<File> fileTree = new HashSet<File>();
        FileFilter fileFilter = new FileFilter() {
            private final String[] acceptedExtensions = new String[]{"jpg", "png", "webp", "jpeg"};

            @Override
            public boolean accept(File file) {
                if (file.isDirectory()) {
                    return true;
                }
                for (String extension : acceptedExtensions) {
                    if (file.getName().toLowerCase().endsWith(extension)) {
                        return true;
                    }
                }
                return false;
            }
        };
        File[] listed = dir.listFiles(fileFilter);
        if(listed!=null){
            for (File entry : listed) {
                if (entry.isFile()) {
                    fileTree.add(entry);
                } else if(recursive){
                    fileTree.addAll(listFileTree(entry,true));
                }
            }
        }
        return new ArrayList<>(fileTree);
    }

List<Path> filePaths = Files
    .find(Paths.get(dir), Integer.MAX_VALUE, (filePath, fileAttr) -> fileAttr.isRegularFile() || fileAttr.isDirectory())
    .collect(Collectors.toList());

filePaths will have files and folder list which can be iterated and proceed further.

    private void fillFilesRecursively(File file, List<File> resultFiles) {
        if (file.isFile()) {
            resultFiles.add(file);
        } else {
            for (File child : file.listFiles()) {
                fillFilesRecursively(child, resultFiles);
            }
        }
    }

Kotlin has FileTreeWalk for this purpose. For example:

dataDir.walkTopDown().filter { !it.isDirectory }.joinToString("\n") {
   "${it.toRelativeString(dataDir)}: ${it.length()}"
}

Will produce a text list of all the non-directory files under a given root, one file per line with the path relative to the root and length.

The accepted answer is great, however it breaks down when you want to do IO inside the lambda.

Here is what you can do if your action declares IOExceptions.

You can treat the filtered stream as an Iterable, and then do your action in a regular for-each loop. This way, you don't have to handle exceptions inside a lambda.

try (Stream<Path> pathStream = Files.walk(Paths.get(path))
        .filter(Files::isRegularFile)) {

    for (Path file : (Iterable<Path>) pathStream::iterator) {
        // something that throws IOException
        Files.copy(file, System.out);
    }
}

Found that trick here: https://stackoverflow.com/a/32668807/1207791

Another way you can do even if someone already provide Java 8 walk.

This one will provide you all files recursively

  private Stream<File> files(File file) {
    return file.isDirectory()
            ? Arrays.stream(file.listFiles()).flatMap(this::files)
            : Stream.of(file);
}

public static String getExten(String path) {
    int i = path.lastIndexOf('.');
    if (i > 0) {
       return path.substring(i);
    }
    else return "";
}
public static List<String> GetAllFiles(String path, List<String>fileList){
    File file = new File(path);
    
    File[] files = file.listFiles();
    for(File folder:files) {
        if(extensions.contains(getExten(folder.getPath()))) {
            fileList.add(folder.getPath());
        }
    }
    File[] direcs = file.listFiles(File::isDirectory);
    for(File dir:direcs) {
        GetAllFiles(dir.getPath(),fileList);
    }
    return fileList;
    
}

This is a simple recursive function that should give you all the files. extensions is a list of string that contains only those extensions which are accepted. Example extensions = [".txt",".docx"] etc.

The accepted answer is poor because it can result in a resource leak.

Files.walk is backed by DirectoryStreams.

The returned stream encapsulates one or more DirectoryStreams. If timely disposal of file system resources is required, the try-with-resources construct should be used to ensure that the stream's close method is invoked after the stream operations are completed. Operating on a closed stream will result in an IllegalStateException.

A DirectoryStream must be closed as specified in it's javadoc:

A DirectoryStream is opened upon creation and is closed by invoking the close method. Closing a directory stream releases any resources associated with the stream. Failure to close the stream may result in a resource leak. The try-with-resources statement provides a useful construct to ensure that the stream is closed:

Path dir = ...
try (DirectoryStream<Path> stream = Files.newDirectoryStream(dir)) {
    for (Path entry: stream) {
        ...
    }
}

As a result, the true answer is:

try (Stream<Path> stream = Files.walk(Paths.get(path))) {
    // Do something with the stream.
    stream.filter(Files::isRegularFile)
          .forEach(System.out::println);
}

Example outputs *.csv files in directory recursive searching Subdirectories using Files.find() from java.nio:

String path = "C:/Daten/ibiss/ferret/";
    logger.debug("Path:" + path);
    try (Stream<Path> fileList = Files.find(Paths.get(path), Integer.MAX_VALUE,
            (filePath, fileAttr) -> fileAttr.isRegularFile() && filePath.toString().endsWith("csv"))) {
        List<String> someThingNew = fileList.sorted().map(String::valueOf).collect(Collectors.toList());
        for (String t : someThingNew) {
            t.toString();
            logger.debug("Filename:" + t);
        }

    }

Posting this example, as I had trouble understanding howto pass the filename parameter in the #1 example given by Bryan, using foreach on Stream-result -

Hope this helps.

base on @Michael answer, add check whether listFiles return null

static Stream<File> files(File file) {
    return file.isDirectory()
            ? Optional.ofNullable(file.listFiles()).map(Stream::of).orElseGet(Stream::empty).flatMap(MainActivity::files)
            : Stream.of(file);
}

or use Lightweight-Stream-API, which support Android5 & Android6

static Stream<File> files(File f) {
    return f.isDirectory() ? Stream.ofNullable(f.listFiles()).flatMap(MainActivity::files) : Stream.of(f);
}

import java.io.File;

public class Main {
    public static void main(String[] args) {
        loopFiles(new File("C:\\Users\\serge.klimkovitch\\Documents"));
    }

    private static void loopFiles(File element) {
        if (element.isDirectory()) {
            for (File currentFile : element.listFiles()) {
                loopFiles(currentFile);
                System.out.println(currentFile);
            }
        }
    }
}