In what situations is the CopyOnWriteArrayList suitable? [duplicate]

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As stated on this link:

CopyOnWriteArrayList is a concurrent Collection class introduced in Java 5 Concurrency API along with its popular cousin ConcurrentHashMap in Java.

CopyOnWriteArrayList implements List interface like ArrayList, Vector and LinkedList but its a thread-safe collection and it achieves its thread-safety in a slightly different way than Vector or other thread-safe collection class.

As name suggest CopyOnWriteArrayList creates copy of underlying
ArrayList with every mutation operation e.g. add or set. Normally
CopyOnWriteArrayList is very expensive because it involves costly
Array copy with every write operation but its very efficient if you
have a List where Iteration outnumber mutation e.g. you mostly need to
iterate the ArrayList and don’t modify it too often.

Iterator of CopyOnWriteArrayList is fail-safe and doesn’t throw
ConcurrentModificationException even if underlying
CopyOnWriteArrayList is modified once Iteration begins because
Iterator is operating on separate copy of ArrayList. Consequently all
the updates made on CopyOnWriteArrayList is not available to Iterator.

To get the most updated version do a new read like list.iterator();

That being said, updating this collection alot will kill performance. If you tried to sort a CopyOnWriteArrayList you’ll see the list throws an UnsupportedOperationException (the sort invokes set on the collection N times). You should only use this read when you are doing upwards of 90+% reads.

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