public static float[][] readMatrix(String fileName, int userNumber, int itemNumber) {
		float[][] result = new float[userNumber][itemNumber];
		
		try {
			BufferedReader br = new BufferedReader(new InputStreamReader(
					new FileInputStream(fileName)));
			
			String line;
			int index = 0;
			while ((line = br.readLine()) != null) {
				if(index >= userNumber) break;
				String[] temp = line.split("\t");
				for (int j = 0; j < temp.length; j++) {
					result[index][j] = Float.parseFloat(temp[j]);
				}
				index++;
			}
			br.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (NumberFormatException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return result;
	}