code: public static void checkFileOrDirectoryToBeRead(File fileOrDir, String fileDesc)
      {
          if (fileOrDir == null)
              throw new IllegalArgumentException(fileDesc + " must not be null.");
          if (!fileOrDir.exists())
              throw new IllegalArgumentException(fileDesc + " does not exist: " + fileOrDir.getAbsolutePath());
          if (!(fileOrDir.isDirectory() || fileOrDir.isFile()))
              throw new IllegalArgumentException(fileDesc + " must be a file or a directory: " + fileOrDir.getPath());
          if (fileOrDir.isDirectory())
          {
              if (fileOrDir.list().length == 0)
                  throw new IllegalArgumentException(fileDesc + " is an empty directory: " + fileOrDir.getPath());
          }
      }
docs: Throws if the given file is null, is not a file or directory, or is an empty directory.