"In designing multithreaded components, you need to consider exactly how the component responds to interaction with other threads. Do you give hard or soft guarantees - for example the view of the size of a multithreaded collection depends on whether you want to be quick and just return the local thread's current impression of the collection size, or do you want to be thorough but slow and give the completely accurate size across all threads (which means suspending element additions and removals until the sizing operation completes! This is a design decision (not implementation), and has definite performance consenqences. It may be worth providing multiple methods, some with hard guarantees and others with soft guarantees so the developer can choose what is best for them."
