Truly Random UUID example

    import java.util.ArrayList;
    import java.util.List;
    import java.util.UUID;
    
    public class Example {
    
        /**
         * A final List<String> of all previous UUIDs generated with
         * generateUniqueID(), turned into a string with uuid.toString();
         */
        private static final List<String> PREVIOUS = new ArrayList<String>();
    
        /**
         * Generates a truly unique UUID.
         * 
         * @param previous
         *            A List<String> of previous UUIDs, converted into a string with
         *            uuid.toString();
         * @return a UUID generated with UUID.randomUUID(); that is not included in
         *         the given List<String>.
         */
        public static UUID generateUniqueID(List<String> previous) {
            UUID u = UUID.randomUUID();
            if (previous.contains(u.toString())) {
                return generateUniqueID(previous);
            }
            return u;
        }
    
        /**
         * Generates a truly unique UUID using the final List<String> PREVIOUS
         * variable defined at the top of the class.
         * 
         * @return A truly random UUID created with generateUniqueID(List<String>
         *         previous);
         */
        public static UUID generateUniqueID() {
            UUID u = generateUniqueID(PREVIOUS);
            PREVIOUS.add(u.toString());
            return u;
        }
    
    }