Question

Is this a valid way to find and remove item from a LinkedList in Java using a for each loop, is it possible that inconsistency may arise:

for(ObjectType ob : obList) {
  if(ob.getId() == id) {
    obList.remove(ob);
    break;
   }
}

Answer 1

Others have mentioned the valid point that normally this is not how you remove an object from a collection. HOWEVER, in this case it’s fine since you break out of the loop once you remove.

If you want to keep iterating after a remove, though, you need to use an iterator. Otherwise you’ll get a ConcurrentModificationException, or in the more general case, undefined behavior.

So yes, if you break out of the foreach after you remove, you’ll be fine.

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To those who’s saying that this will fail because you can’t modify a collection in a foreach — this is true only if you want to keep iterating. That’s not the case here, so this shortcut is fine.

A ConcurrentModificationException is checked and thrown by the iterator. Here, after the remove (which qualifies as concurrent modification), you break out of the loop. The iterator doesn’t even get a chance to detect it.

It may be best if you add a comment on the break, why it’s absolutely necessary, etc, because if this code is later modified to continue iterating after a remove, it will fail.

I would treat this idiom similar to goto (or rather, labeled break/continue): it may seem wrong at first, but when used wisely, it makes for a cleaner code.