如何在一个有许多子文件夹的目录中检索一个文件，而不使用批处理文件逐个声明它们？

function searchFile(directory, filename):
    files = listFiles(directory)
    for file in files:
        if file is a directory:
            filePath = searchFile(file, filename)
            if filePath is not None:
                return filePath
        else if file is the target file:
            return file path
    return None

import os

def search_file(directory, filename):
    for root, dirs, files in os.walk(directory):
        if filename in files:
            return os.path.join(root, filename)
    return None

import java.io.File;

public class FileSearcher {
    public static String searchFile(String directory, String filename) {
        File dir = new File(directory);
        File[] files = dir.listFiles();
        if (files != null) {
            for (File file : files) {
                if (file.isDirectory()) {
                    String filePath = searchFile(file.getAbsolutePath(), filename);
                    if (filePath != null) {
                        return filePath;
                    }
                } else if (file.getName().equals(filename)) {
                    return file.getAbsolutePath();
                }
            }
        }
        return null;
    }
}