code: public static void concatenate(List<File> files, File concatenatedFile) {
  
          BufferedWriter writer;
          try {
              writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(concatenatedFile.getAbsoluteFile(),
                      false), DataUtilDefaults.charSet));
  
              FileInputStream inputStream;
              for(File input : files) {
                  inputStream = new FileInputStream(input);
                  BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
                  String line;
                  while((line = reader.readLine()) != null) {
                      writer.write(line + DataUtilDefaults.lineTerminator);
                  }
                  inputStream.close();
              }
              writer.flush();
              writer.close();
          } catch (UnsupportedEncodingException e) {
              throw new DataUtilException(e);
          } catch (FileNotFoundException e) {
              throw new DataUtilException(e);
          } catch (IOException e) {
              throw new DataUtilException(e);
          }
      }
docs: This method will concatenate one or more files
  @param files files to concatenate
  @param concatenatedFile concatenated output file