"Stream-based code is certainly not something you can read off the cuff."

    List<Integer> transactionsIds = 
        transactions.stream()
                    .filter(t -> t.getType() == Transaction.GROCERY)
                    .sorted(comparing(Transaction::getValue).reversed())
                    .map(Transaction::getId)
                    .collect(toList());

I honestly think most programmers fluent in Java 7 programming, can guess this is finding "grocery" type transactions, sorting by "value" transaction property in descending order, extracting the transaction ids, and returning the result as a list. ("map" could be confusing, as this usage is borrowed from functional programming.)

May take a while to learn the performance and memory usage characteristics, and how to correctly write code in this style, but I'm not buying that it is difficult to "read off the cuff."