code: public File[] listFiles(String directoryPath) {
          File[] result = null;
          File directory = null;
          directory = new File(directoryPath);
          if (directory.isDirectory()) {
              result = directory.listFiles();
          }
          return result;
      }
docs: Get the list of files within the given directory. This only returns the
  files in the immediate directory and is not recursive.
  
  @param directoryPath The path of the directory
  
  @return The list of files in the directory
  
  @see File#listFiles()