Caffeine Cache - Updating a collection

Question

I'm working on a Kafka record consumer and comparator. I'm using caffeine to store the consumed messages with a unique I'd for later comparison. Here's a simplified example.

// Spring cache configuration
Cache<String, LinkedList<Data>> cache = Caffeine.newBuilder().build();

// Consumer // determine if already present code above.
LinkedList<Data> dataLinkedList = cache.getIfPresent("KEY");

// Directly update the list with consumed data ordered by timestamp on Data object (mocked in this example).
dataLinkedList.add(new Data(UUID.randomUUID().toString(), rand.nextLong(1000) - 10));

Is this approach of directly updating the list reference completely stupid or do I have to call put again with the new collection. The application is not mutli-threaded.

Following @Ben Manes suggestion I added this

public static BiFunction<String, LinkedList<Data>, LinkedList<Data>> mapperFunc(Data data) {
        return (key, list) -> {
            int current;
            for (current = 0; current < list.size(); current++) {
                if(data.timeStamp() > list.get(current).timeStamp())
                    break;
            }
            list.add(current, data);
            return list;
        };
    }

// add elements
cache.asMap().compute("KEY", mapperFunc(new Data(UUID.randomUUID().toString(), 1234)));