in class recursion

public class FilesUtils {

    public static void traverseDirectories(String path) {
        File dir = new File(path);
        File[] allFiles = dir.listFiles();
        if (allFiles == null) {
            return;
        }
        if (allFiles.length == 0) {
            return;
        }
        System.out.println(dir.getName() + ":");

        String indent = "";
        traverseRecursive(allFiles, indent);
    }

    private static void traverseRecursive(File[] list, String indent) {
        if (list == null) return;
        if (list.length == 0) return;
        indent += " ";
        for (File file : list) {
            if (file.isDirectory()) {
                System.out.println(indent + file.getName() + ":");
                traverseRecursive(file.listFiles(), indent);
            }
            if (file.isFile()) {
                System.out.println(indent + file.getName());
            }
        }
    }

    public static List<String> findFiles(String path, String extension) {
        File fileSearch = new File(path);
        File[] allFiles = fileSearch.listFiles();
        List<String> result = new ArrayList<>();
        if (allFiles == null) {
            return result;
        }
        if (allFiles.length == 0) {
            return result;
        }
        for (File file : allFiles) {
            if (file.isDirectory()) {
                result.addAll(findFiles(file.toString(), extension));
            } else {
                if (file.getName().endsWith(extension)) {
                    result.add(file.getName());
                }
            }
        }
        return result;
    }

    public static boolean fileExists(String path, String fileName) {
        File dir = new File(path);
        File[] allFilesInDir = dir.listFiles();
        boolean fileNameExist = false;

        if (allFilesInDir == null || allFilesInDir.length == 0) {
            return false;
        }
        for (File file : allFilesInDir) {
            if (file.isDirectory()) {
                fileNameExist = fileExists(file.toString(), fileName);
            }
            if (file.getName().equals(fileName)) {
                return true;
            }
        }
        return fileNameExist;
    }