public static void createData(String fileName, int fileNumber) throws IOException {
		Random random = new Random();
		BufferedWriter bw = new BufferedWriter(new FileWriter(fileName));
		
		for (int idx = 1 ; idx <= NUM_USERS / NUM_FILES ; idx++) {
			String output = "";
			
			int birth1 = random.nextInt(100);
			int birth2 = random.nextInt(12) + 1;
			int birth3 = random.nextInt(30) + 1;
			
			int id  = fileNumber * NUM_USERS + idx;
			
			int phone2 = random.nextInt(9000) + 1000;
			int phone3 = random.nextInt(10000);
			
			// id
			output += String.format("%02d", birth1) + String.format("%02d", birth2) + String.format("%02d", birth3)
					+ "-" + String.format("%07d", id) + ",";
			
			// name
			output += getRandomString(random, 5) +  ",";
			
			// phone number
			output += String.format("%03d", 10) + "-" + String.format("%04d", phone2) + "-"
					+ String.format("%04d", phone3) + ",";
			
			// addr
			output += getRandomString(random, 50) +  "\n";
			
			bw.write(output);
		}
		
		bw.close();
	}