public static  ArrayList<String> splitFile() throws IOException{
		DataHandler.cleanDir(preprocessFolder);
		ArrayList<String> fileList=DataHandler.getFileList(DataHandler.originFolder);
		int fileTag=0;
		int lineCnt=0;
		BufferedReader br = null;
		BufferedWriter bw = null;
		for(int i=0;i<fileList.size();i++){
			File file=new File(fileList.get(i));
			try {
				br = new BufferedReader(new FileReader(file));
				//br.readLine();//discard the 1st line of csv file
			} catch (IOException e) {
				e.printStackTrace();
			}
			String line;
			try {
				File splitFile=new File(DataHandler.preprocessFolder+Integer.toString(fileTag)+"_"+Integer.toString(i)+".txt");
				bw=new BufferedWriter(new OutputStreamWriter(new FileOutputStream(splitFile)));
				while ((line = br.readLine()) != null ){
					
					bw.write(line);
					bw.write("\r\n");
					lineCnt++;
					if(lineCnt>=threshold){
						bw.flush();
						bw.close();
						fileTag++;
						splitFile=new File(DataHandler.preprocessFolder+Integer.toString(fileTag)+"_"+Integer.toString(i)+".txt");
						bw=new BufferedWriter(new OutputStreamWriter(new FileOutputStream(splitFile)));
						lineCnt=0;
					}
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				br.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		bw.flush();
		bw.close();
		ArrayList<String> splitFileList=DataHandler.getFileList(DataHandler.preprocessFolder);
		return splitFileList;	
	}