Which method of Iterator throws ConcurrentModificationException?

The iterators returned by ArrayList 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 .

How do I stop ConcurrentModificationException?

We can also avoid the Concurrent Modification Exception in a single threaded environment. We can use the remove() method of Iterator to remove the object from the underlying collection object. But in this case, you can remove only the same object and not any other object from the list.

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.

What causes Java Util ConcurrentModificationException?

Class ConcurrentModificationException. This exception may be thrown by methods that have detected concurrent modification of an object when such modification is not permissible. For example, it is not generally permissible for one thread to modify a Collection while another thread is iterating over it.

Why Iterator is fail fast?

Iterator on ArrayList, HashMap classes are some examples of fail-fast Iterator. 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. Iterator on CopyOnWriteArrayList, ConcurrentHashMap classes are examples of fail-safe Iterator.

Does Iterator throw a ConcurrentModificationException?

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

Can we remove an element by using for each loop?

The program needs access to the iterator in order to remove the current element. The for-each loop hides the iterator, so you cannot call remove .

Does iterator throw a ConcurrentModificationException?

Can we update HashMap while iterating?

Well, you can’t do it by iterating over the set of values in the Map (as you are doing now), because if you do that then you have no reference to the keys, and if you have no reference to the keys, then you can’t update the entries in the map, because you have no way of finding out which key was associated with the …

What is the difference between HashMap and ConcurrentHashMap?

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.

Which browser uses least memory?

1- Microsoft Edge The dark horse topping our list of browsers using the least RAM space is none other than Microsoft Edge. Gone are the days of Internet Explorer with bugs and exploitations galore; now, with a Chromium engine, things are looking up for Edge.

What does java.util.ConcurrentModificationException mean in Java?

java.util.ConcurrentModificationException is a very common exception when working with Java collection classes. Java Collection classes are fail-fast, which means if the Collection will be changed while some thread is traversing over it using iterator, the iterator.next () will throw ConcurrentModificationException.

How to avoid ConcurrentModificationException in multi-threaded environment?

To avoid the ConcurrentModificationException in a multi-threaded environment, we can follow the following ways- Instead of iterating over the collection class, we can iterate over the array. In this way, we can work very well with small-sized lists, but this will deplete the performance if the array size is very large.

When does an iterator throw an exception in Java?

This may happen when a thread is trying to modify the Collection object while it is being iterated by some fail-fast iterator, the iterator will throw the exception. This message says that the exception is thrown when the next method is called as the iterator is iterating the list and we are making modifications in it simultaneously.

How to avoid concurrent modification exception in jdk1.5?

This approach is not recommended because it will cease the benefits of multithreading. If you are using JDK1.5 or higher then you can use ConcurrentHashMap and CopyOnWriteArrayList classes. This is the recommended approach to avoid concurrent modification exception.