What is a concurrent modification exception?
What is a concurrent modification exception?
The ConcurrentModificationException occurs when an object is tried to be modified concurrently when it is not permissible. This exception usually comes when one is working with Java Collection classes. For Example – It is not permissible for a thread to modify a Collection when some other thread is iterating over it.
What Iterator can throw concurrent modification exception?
If we invoke a sequence of methods on an object that violates its contract, then the object throws ConcurrentModificationException. For example: if while iterating over the collection, we directly try to modify that collection, then the given fail-fast iterator will throw this ConcurrentModificationException.
How do you resolve concurrent modification exception?
How do you fix Java’s ConcurrentModificationException? There are two basic approaches: Do not make any changes to a collection while an Iterator loops through it. If you can’t stop the underlying collection from being modified during iteration, create a clone of the target data structure and iterate through the clone.
How Iterator knows about ConcurrentModificationException?
Iterator fail-fast property checks for any modification in the structure of the underlying collection everytime we try to get the next element. If there are any modifications found, it throws ConcurrentModificationException.
Why is there no concurrent modification exception in ConcurrentHashMap?
ConcurrentHashMap does not throw ConcurrentModificationException if the underlying collection is modified during an iteration is in progress. Iterators may not reflect the exact state of the collection if it is being modified concurrently.
What is the concurrent modification exception in Java stack overflow?
For example, if a thread modifies a collection directly while it is iterating over the collection with a fail-fast iterator, the iterator will throw this exception.
What Iterator can throw a concurrent modification exception Mcq?
The Fail Fast iterator throws a ConcurrentModificationException if a collection is modified while iterating over it. The Fail Fast iterator uses an original collection to traverse over the collection’s elements.
How do you prevent concurrent modification exception on a map?
- make your POJOs thread-safe and do data updates on POJOs directly.
- use ConcurrentHashMap.
- keep on using simple HashMap, but build a new map on each modification and switch maps behind the scenes (synchronizing the switch operation or using AtomicReference)
Can ConcurrentHashMap throws ConcurrentModificationException?
What is difference between Iterator and ListIterator?
The basic difference between Iterator and ListIterator is that both being cursor, Iterator can traverse elements in a collection only in forward direction. On the other hand, the ListIterator can traverse in both forward and backward directions. You can retrieve an index of an element using Iterator.
What is fail fast and fail safe?
Difference Between Fail Fast and Fail Safe Iterators The Major difference between Fail Fast and Fail Safe iterator is that the Fail Safe does not throw any ConcurrentModificationException in modifying the object during the iteration process, contrary to fail fast, which throws an exception in such scenarios.
