code: public static Collection<String> listFiles(String filesString, String delimiter) {
      ValidationUtils.validateNotEmpty(filesString, "fileStr");
  
      List<String> files = new ArrayList<String>();
      for (String fileString : filesString.split(delimiter)) {
        File file = new File(fileString);
        if (!file.getName().contains("*") && !file.getName().contains("?")) {
          files.add(file.getAbsolutePath());
          continue;
        }
  
        FileFilter fileFilter = new AndFileFilter(new WildcardFileFilter(file.getName()),
            FileFileFilter.FILE);
        File parent = file.getParentFile() == null ? file : file.getParentFile();
        File[] filteredFiles = parent.listFiles(fileFilter);
        if (filteredFiles == null) {
          continue;
        }
  
        for (File filteredFile : filteredFiles) {
          files.add(filteredFile.getAbsolutePath());
        }
      }
      return files;
    }
docs: Find files while input can use wildcard * or ?
  
  @param filesString File path(s) delimited by delimiter
  @param delimiter Separator of file paths.
  @return List of absolute path of files