code: public static void textToBinary(String featuresFolder, final String featureType, int featureLength)
  			throws Exception {
  		// read the folder containing the description files
  		File dir = new File(featuresFolder);
  		FilenameFilter filter = new FilenameFilter() {
  			public boolean accept(File dir, String name) {
  				if (name.endsWith("." + featureType))
  					return true;
  				else
  					return false;
  			}
  		};
  		String[] files = dir.list(filter);
  
  		for (int i = 0; i < files.length; i++) {
  			if (i % 100 == 0) {
  				System.out.println("Converting file " + i);
  			}
  			BufferedReader in = new BufferedReader(new FileReader(new File(featuresFolder + files[i])));
  			DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(
  					featuresFolder + files[i] + "b")));
  			String line;
  			while ((line = in.readLine()) != null) {
  				String[] nums = line.split(",");
  				for (int j = 0; j < featureLength; j++) {
  					out.writeDouble(Double.parseDouble(nums[j]));
  				}
  			}
  			in.close();
  			out.close();
  		}
  	}
docs: Takes a folder with feature files in text format and converts them to binary.
  
  @param featuresFolder
  @param featureType
  @param featureLength
  @throws Exception