What is Java Util ConcurrentModificationException?

How do I fix ConcurrentModificationException in Java?

How to avoid ConcurrentModificationException in a multi-threaded environment?

  1. Instead of iterating over the collection class, we can iterate over the array. …
  2. Another way can be locking the list by putting it in the synchronized block. …
  3. JDK 1.5 or higher provides with ConcurrentHashMap and CopyOnWriteArrayList classes.

Which method of iterator throws ConcurrentModificationException?

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.

Does HashMap throw ConcurrentModificationException?

You cannot remove an entry while looping over Map but you can remove a key or value while iterating over it. Since Iterator of HashMap is fail-fast it will throw ConcurrentModificationException if you try to remove entry using Map.

Does iterator throw a ConcurrentModificationException?

ConcurrentModificationException is not thrown by Iterator. remove() because that is the permitted way to modify an collection while iterating.

What is fail safe in Java?

Fail-safe iterators allow modifications of a collection while iterating over it. These iterators don’t throw any Exception if a collection is modified while iterating over it. They use copy of original collection to traverse over the elements of the collection.

IT IS INTERESTING:  You asked: What is Dependency Injection in Java?

What is difference between HashMap and ConcurrentHashMap in Java?

HashMap is non-Synchronized in nature i.e. HashMap is not Thread-safe whereas ConcurrentHashMap is Thread-safe in nature. HashMap performance is relatively high because it is non-synchronized in nature and any number of threads can perform simultaneously.

How can we avoid ConcurrentModificationException in a multi-threaded environment?

To Avoid ConcurrentModificationException in multi-threaded environment

  1. You can convert the list to an array and then iterate on the array. …
  2. You can lock the list while iterating by putting it in a synchronized block. …
  3. If you are using JDK1.

Is iterator thread-safe in Java?

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.

Can we convert HashMap to ConcurrentHashMap?

Synchronize HashMap – ConcurrentHashMap

ConcurrentHashMap support concurrent access to it’s key-value pairs by design. We do not need to perform any additional code modifications to enable synchronization on the map.

Is ConcurrentHashMap remove thread-safe?

ConcurrentHashMap class is thread-safe i.e. multiple threads can operate on a single object without any complications. … In ConcurrentHashMap, at a time any number of threads can perform retrieval operation but for updated in the object, the thread must lock the particular segment in which the thread wants to operate.

What is the root cause for Java Util ConcurrentModificationException?

The java. util. ConcurrentModificationException is typically thrown when code attempts to modify a data collection while that collection is actively in use, such as being iterated.

IT IS INTERESTING:  What are the clauses of a basic query in SQL?
Categories PHP