Frequent question: What is Java Util ConcurrentModificationException null?

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.

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.

How can we avoid ConcurrentModificationException in a single threaded environment?

To Avoid ConcurrentModificationException in single-threaded environment. You can use the iterator remove() function to remove the object from underlying collection object. But in this case, you can remove 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 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.

IT IS INTERESTING:  Question: Is Tsql same as SQL Server?

What is CopyOnWriteArrayList in Java?

CopyOnWriteArrayList is a thread-safe variant of ArrayList where operations which can change the ArrayList (add, update, set methods) creates a clone of the underlying array. CopyOnWriteArrayList is to be used in a Thread based environment where read operations are very frequent and update operations are rare.

What is Iterator in Java?

Iterator in Java. In Java, an Iterator is one of the Java cursors. Java Iterator is an interface that is practiced in order to iterate over a collection of Java object components entirety one by one. … The Java Iterator also helps in the operations like READ and REMOVE.

Is ArrayList thread-safe?

Vectors are synchronized. Any method that touches the Vector ‘s contents is thread safe. ArrayList , on the other hand, is unsynchronized, making them, therefore, not thread safe. … So if you don’t need a thread-safe collection, use the ArrayList .

What is Java Util ConcurrentModificationException?

The java. util. concurrentmodificationexception is an error in Java. The error occurs when the iterator is traversing a list, and a command is used to change an element’s value during that traversal.

How does ConcurrentHashMap works in Java?

ConcurrentHashMap class is thread-safe i.e. multiple threads can operate on a single object without any complications. … In ConcurrentHashMap, the Object is divided into a number of segments according to the concurrency level. The default concurrency-level of ConcurrentHashMap is 16.

Can we iterate HashMap?

There is a numerous number of ways to iterate over HashMap of which 5 are listed as below: Iterate through a HashMap EntrySet using Iterators. Iterate through HashMap KeySet using Iterator. Iterate HashMap using for-each loop.

IT IS INTERESTING:  How do you write a decorator in TypeScript?
Categories JS