exception java util concurrentmodificationexception

understanding `concurrentmodificationexception`

1. **why it occurs**: when you modify a collection while iterating over it using methods like `for-each`, `iterator`, etc., the underlying structure of the collection might change, leading to unpredictable behavior and data inconsistency. java uses a fail-fast mechanism, which means that if a thread detects that a collection has been modified (except through the iterator's own `remove` method), it throws a `concurrentmodificationexception`.

2. **common scenarios**:
- using a `for-each` loop to iterate over a collection and modifying it within the loop.
- using multiple threads that modify the same collection without proper synchronization.

example of `concurrentmodificationexception`

here’s a simple example illustrating how a `concurrentmodificationexception` occurs:

output

when you run the above code, you will get an output similar to:

how to avoid `concurrentmodificationexception`

1. **using `iterator`'s `remove()` method**:
instead of directly modifying the collection, you can use the `iterator` to safely remove elements.



2. **using `copyonwritearraylist`**:



summary

- **`concurrentmodificationexception`** is a runtime exception that occurs when a collection is modified while it is being iterated.
- it helps to prevent inconsistent data states in collections.
- you can avoid this exception by using the `iterator`'s ...

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