Is there a way to remove a custom Object from every occurrence?

Question

I'm trying to remove every GameObject which meet certain criteria (health<0), completely from every occurrence, so every ArrayList it might be in, and such.

I have a main ArrayList containing every GameObject that may get removed, and I'm trying to iterate through that ArrayList with a For-Each, checking each element for the criteria, and removing it.

This however results in ConcurrentModificationException, which I know the reason to, but do not know how to work around it. Any help would be much appreciated!

Use iterator to do that as iterator.remove() will not cause taht exception. — Antoniossss, Apr 25 '19 at 13:38
See [`Collection#removeIf`](https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/util/Collection.html#removeIf(java.util.function.Predicate)) — Jacob G., Apr 25 '19 at 13:38
Just initialize the ArrayList like this: `Collections.synchronizedList(new ArrayList());` — NeplatnyUdaj, Apr 25 '19 at 13:39
@Lino You're right of course, I didn't read carefully. Thought that the issue is from some other thread modifying the array, not that the removal algorithm is wrong from the start. — NeplatnyUdaj, Apr 25 '19 at 14:32

score 2 · Accepted Answer · answered Apr 25 '19 at 13:59

As @JacobG. mentioned in his comment, perhaps the "best" way to do this (where "best" is going to be a matter of personal preference) is via the .removeIf() method. Here's an example (which assumes a getHealth() method on your objects):

List<GameObject> gameObjects = new ArrayList<>();

// Some code here to populate the list

gameObjects.removeIf(x -> x.getHealth() < 0);

score 0 · Answer 2 · answered Apr 25 '19 at 13:57

if you have all the items to be removed in a separate ArrayList, you could use CollectionUtils.subtract() method from apache-commons-collections to remove them from other lists :

yourList = (ArrayList<GameObject>)CollectionUtils.subtract(yourList, listWithObjectsToRemove);

See this link

Is there a way to remove a custom Object from every occurrence?

2 Answers2