code: public void setInput(final String input) {
          if (input == null) {
              throw (new IllegalArgumentException(
                      "You must provide a COBOL source folder or file"));
          }
          File file = new File(input);
          if (file.exists()) {
              if (file.isDirectory() && file.list().length == 0) {
                  throw new IllegalArgumentException("Folder " + input
                          + " is empty");
              }
          } else {
              throw new IllegalArgumentException("Input file or folder " + input
                      + " not found");
          }
          _input = file;
      }
docs: Check the input parameter and keep it only if it is valid.
  
  @param input a file or folder name (relative or absolute)