This week's book giveaway is in the Agile and Other Processes forum. We're giving away four copies of Real-World Software Development: A Project-Driven Guide to Fundamentals in Java and have Dr. Raoul-Gabriel Urma & Richard Warburton on-line! See this thread for details.
Management of a collection of CodeRanchUser objects should be encapsulated in its own class, e.g. CodeRanchUsers (plural).
Line 16, don't need toString() call.
Line 30, why the trailing space?
Users should be added through CodeRanchUsers which should return an ID. From there on all access should be via the ID and not an ordinal position in the List because CodeRanchUsers may or may not choose to implement a List. So the use of get(3), for example, would be replaced by a retrieval by ID.