code: private void createSourceMapFile(File output,SourceMap sourceMap) throws WatchingException{
          if (googleClosureMap) {
              PrintWriter mapWriter = null;
              File mapFile = new File(output.getPath() + ".map");
              FileUtils.deleteQuietly(mapFile);
  
              try {
                  mapWriter = new PrintWriter(mapFile, Charset.defaultCharset().name());
                  sourceMap.appendTo(mapWriter, output.getName());
                  FileUtils.write(output, "\n//# sourceMappingURL=" + mapFile.getName(), true);
              } catch (IOException e) {
                  throw new WatchingException("Cannot create source map file for JavaScript file '" +
                          output.getAbsolutePath() + "'", e);
              } finally {
                  IOUtils.closeQuietly(mapWriter);
              }
          }
      }
docs: Create a source map file corresponding to the given compiled js file.
  
  @param output The compiled js file
  @param sourceMap The {@link SourceMap} retrieved from the compiler
  @throws WatchingException If an IOException occurred while creating the source map file.