public static String valueOfString(String i, int length) {
		int size = i.length();
		if (size >= length) {
			return i;
		}
		int leadingZeroCount = length - size;
		char[] zeros = new char[leadingZeroCount];
		Arrays.fill(zeros, '0');

		StringBuilder buffer = new StringBuilder();
		buffer.append(zeros);
		buffer.append(i);
		
		String s = buffer.toString();
		buffer.setLength(0);
		buffer = null;
		return s;
	}