private Map<String, Double> getCateWordsNum(String trainDir) throws IOException {
		// TODO Auto-generated method stub
		Map<String,Double> cateWordsNum = new TreeMap<String,Double>();
		File[] sampleDir = new File(trainDir).listFiles();
		for(int i = 0; i < sampleDir.length; i++){
			double count = 0;
			File[] sample = sampleDir[i].listFiles();
			for(int j = 0;j < sample.length; j++){
				FileReader spReader = new FileReader(sample[j]);
				BufferedReader spBR = new BufferedReader(spReader);
				while(spBR.readLine() != null){
					count++;
				}		
			}
			cateWordsNum.put(sampleDir[i].getName(), count);
		}
		return cateWordsNum;
	}