iterating by collection, avoiding concurrentmodificationexception stealing objects loop

we know can't following since concurrentmodificationexception:

for (object i : l) {
    (condition(i)) {
        l.remove(i);
    }
}

but apparently works sometimes, nonetheless always. here's specific code:

public stationary vacant main(string[] args) {
    collection<integer> l = new arraylist<>();

    (int i = 0; i < 10; ++i) {
        l.add(4);
        l.add(5);
        l.add(6);
    }

    (int i : l) {
        (i == 5) {
            l.remove(i);
        }
    }

    system.out.println(l);
}

this, course, law in:

exception thread "main" java.util.concurrentmodificationexception

even nonetheless churned threads aren't doing it. anyway.

what's best fortitude problem? i mislay an vigilant collection loop but throwing exception?

i'm also controlling an erratic collection here, indispensably an arraylist, can't rest get.