Recursively list files in Java

Question

How do I recursively list all files under a directory in Java? Does the framework provide any utility?

I saw a lot of hacky implementations. But none from the fra

Answer 1

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

 public static ArrayList listFileTree(File dir,boolean recursive) {
        if (null == dir || !dir.isDirectory()) {
            return new ArrayList<>();
        }
        final Set fileTree = new HashSet();
        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);
    }