Difference between fail fast/fail safe collections
In the context of programming, particularly in Java, "fail-fast" and "fail-safe" are terms used to describe how collections (like lists, sets, and maps) handle concurrent modifications while iterating over them. Here’s a breakdown of the differences between the two:
Definition: Fail-fast collections immediately throw a ConcurrentModificationException
if they detect that the collection has been modified (structurally) after the iterator was created, except through the iterator's own methods.
Behavior:
Examples:
ArrayList
, HashMap
, and HashSet
are examples of fail-fast collections.Use Case:
Definition: Fail-safe collections allow for concurrent modifications without throwing an exception. Instead of throwing an error, they provide a snapshot of the collection at the time the iterator was created.
Behavior:
Examples:
CopyOnWriteArrayList
and ConcurrentHashMap
are examples of fail-safe collections.Use Case:
ConcurrentModificationException
on concurrent modifications; suitable for single-threaded scenarios.Choosing between fail-fast and fail-safe collections depends on the specific requirements of your application, particularly regarding concurrency and performance.