只能从main（）读取文件夹/目录？(can only read folder/directory from main() ? listfiles() returns null?)

 我正在x64 windows操作系统上使用jdk 1.8 x64开发Netbeans java项目我的问题是：“如果从我的TextProcessor类实例调用，则使用file.listfolders()方法读取目录的内容（仅限文件）。 ，将方法更改为static并从main()调用它可以完美地工作，所以它与权限无关，据我了解。 
 
private List<String> get_files_paths(String data_path) {
    File folder = new File(data_path);
    List<String> full_paths = new ArrayList<String>();
    for (final File fileEntry : folder.listFiles()) {
        if (!fileEntry.isDirectory())
            full_paths.add(fileEntry.getAbsolutePath());
    }
    return full_paths;
}
 
 提前致谢。 

I'm working on a Netbeans java project using jdk 1.8 x64 on a x64 windows OS My problem is: "reading a directory's content (only files) with the method file.listfolders() outputs null if called from my TextProcessor class instance. However, changing the method to static and calling it from a main() works perfectly, so it has nothing to do with permissions as far as I understand.
 
private List<String> get_files_paths(String data_path) {
    File folder = new File(data_path);
    List<String> full_paths = new ArrayList<String>();
    for (final File fileEntry : folder.listFiles()) {
        if (!fileEntry.isDirectory())
            full_paths.add(fileEntry.getAbsolutePath());
    }
    return full_paths;
}
 
Thanks in advance.

原文：https://stackoverflow.com/questions/43803197