A simple GUID generating function

GUIDFactory.java

public class GUIDFactory {
	private static final String chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	private static final int charsCount = chars.length();

	/**
	 * Generates a random GUID. Example :
	 * 
	 * <pre>
	 * 13219ec0-3a81-44c5-a300-de14b7d0235f
	 * </pre>
	 * 
	 * @return A global unique identifier as a String
	 */
	public static String next(int length) {
		String guid = "";
		int cmp = 0;

		for (int i = 0; i < length; i++) {
			cmp = (int) (Math.round(Math.random() * 255) - 128) & 255;

			if (i == 6) {
				cmp = cmp & (charsCount - 1);
				cmp = cmp | (4 << 4);
			}

			if (i == 8) {
				cmp = cmp & 63;
				cmp = cmp | 128;
			}

			guid += chars.charAt(cmp >> 4);
			guid += chars.charAt(cmp & (charsCount - 1));
		}

		return guid;
	}

}