Is iterator fail safe?Asked by: Samantha Jones | Last update: 18 June 2021
Score: 5/5 (45 votes)
Fail-Safe iterators don't throw any exceptions if a collection is structurally modified while iterating over it. This is because, they operate on the clone of the collection, not on the original collection and that's why they are called fail-safe iterators.View full answer
Furthermore, What is fail fast and fail safe iterator?
The Java Collection supports two types of iterators; Fail Fast and Fail Safe. These iterators are very useful in exception handling. The Fail fast iterator aborts the operation as soon it exposes failures and stops the entire operation. Comparatively, Fail Safe iterator doesn't abort the operation in case of a failure.
Simply so, Why ConcurrentHashMap is fail safe?. Iterator of ConcurrentHashMap is fail-safe, it means that it doesn't throw ConcurrentModificationException even if underlying ConcurrentHashMap is modified once Iteration begins.
People also ask, Is listIterator fail fast or fail safe?
The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException .
Is iterator thread safe?
No iterator is thread-safe. If the underlying collection is changed amidst iteration, a ConcurrentModificationException is thrown. Even iterators of synchronized collections are not thread-safe - you have to synchronize manually. One exception is the CopyOnWriteArrayList , which holds a snapshot during iteration.
And, importantly, HashMap is not a thread-safe implementation, while Hashtable does provide thread-safety by synchronizing operations. Even though Hashtable is thread safe, it is not very efficient. Another fully synchronized Map, Collections.
ArrayList is non synchronized because if ArrayList is synchronized then only one thread can work on ArrayList at a time and rest of all threads cannot perform other operations on the ArrayList until the first thread release the lock. This causes overhead and reduces performance. This applies for all collections.
Fail-Fast iterators immediately throw ConcurrentModificationException if there is structural modification of the collection. Structural modification means adding, removing any element from collection while a thread is iterating over that collection.
LinkedList - fail-safe or fail-fast iteration using iterator, listIterator, Enumeration and enhanced for loop. iterator returned by LinkedList is fail-fast. Means any structural modification made to LinkedList like adding or removing elements during Iteration will throw java. util.
Iterator of ArrayList is fail fast , so while you are iterating over the ArrayList using the Iterator if underlying ArrayList is modified by any method other than add and remove provided by Iterator itself it will throw ConcurrentModificationException and will bail out.
You should use ConcurrentHashMap when you need very high concurrency in your project. It is thread safe without synchronizing the whole map . Reads can happen very fast while write is done with a lock. There is no locking at the object level.
Fail-safe iterators means they will not throw any exception even if the collection is modified while iterating over it. ... Whereas Fail-fast iterators throw an exception(ConcurrentModificationException) if the collection is modified while iterating over it.
Both Vector and ArrayList use growable array data structure. The iterator and listIterator returned by these classes (Vector and ArrayList) are fail-fast.
Fail fast is the principle of freely experimenting and learning while trying to reach the desired result. By quickly finding the failures, you can catapult learning and optimize solutions instantly to reach your goal. The concept of fail fast is strongly connected to the Agile methodology.
Interviewer : How Fail Fast Iterator come to know that the internal structure is modified ? Iterator read internal data structure (object array) directly . The internal data structure(i.e object array) should not be modified while iterating through the collection. To ensure this it maintains an internal flag "mods" .
ConcurrentHashMap class is thread-safe i.e. multiple threads can operate on a single object without any complications. At a time any number of threads are applicable for a read operation without locking the ConcurrentHashMap object which is not there in HashMap. ... The default concurrency-level of ConcurrentHashMap is 16.
A Fail Fast Exception is a type of Exception made by User Mode applications. ... Unlike all other exception codes, Fail Fast Exceptions bypass all exception handlers (frame or vector based). Raising this exception terminates the application and invokes Windows Error Reporting, if Windows Error Reporting is enabled.
Iterators are used in Collection framework in Java to retrieve elements one by one. There are three iterators. Enumeration : It is a interface used to get elements of legacy collections(Vector, Hashtable). Enumeration is the first iterator present from JDK 1.0, rests are included in JDK 1.2 with more functionality.