code: @SuppressWarnings("nls")
      public static void writeProjectionFile( String filePath, String extention, CoordinateReferenceSystem crs )
              throws IOException {
          /*
           * fill a prj file
           */
          String prjPath = null;
          if (extention != null && filePath.toLowerCase().endsWith("." + extention)) {
              int dotLoc = filePath.lastIndexOf(".");
              prjPath = filePath.substring(0, dotLoc);
              prjPath = prjPath + ".prj";
          } else {
              if (!filePath.endsWith(".prj")) {
                  prjPath = filePath + ".prj";
              } else {
                  prjPath = filePath;
              }
          }
  
          try (BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(prjPath))) {
              bufferedWriter.write(crs.toWKT());
          }
      }
docs: Fill the prj file with the actual map projection.
  
  @param filePath  the path to the regarding data or prj file.
  @param extention the extention of the data file. If <code>null</code>, the crs is written to filePath directly.
  @param crs       the {@link CoordinateReferenceSystem} to write.
  
  @throws IOException