I know that removing an element from a list while iterating it is not recommended.
You better use iterator.remove(), java streams, or copy the remove to an external list.
But this simple code just works:
static List<Integer> list = new ArrayList<Integer>();
...
private static void removeForI() {
for (int i = 0; i < 10; i++) {
if (i == 3) {
list.remove(i);
continue;
}
System.out.println(i);
}
}
Is it safe to use it?
You need to think about how list.remove(index) works.
When remove(idx) gets called, the element at idx index gets deleted and all the next elements gets shifted to left.
So, suppose you have a list containing 2, 3, 3, 4, 5. Now you want to remove all the 3s from this list. But if you use your current approach, it will remove only the first occurrence of 3. Because after removing 1st occurrence of 3 which is at position 1 your contents will get shifted to left and will be like this 2, 3, 4, 5. But now your for loop will increment the current index to 2 which contains 4 and not 3.
That is why it is not advised to remove items while iterating, Because index of items gets changed after each removal.
Edit: Also if you are using a constant value in loop break condition like in above example i<10; you might get ArrayIndexOutOfBounds exception.
System.out.println(list.get(i)); instead of System.out.println(i); inside your loop.Even though it works under the condition people have pointed out, I would only use it temporarily and change it to:
private static void removeForI() {
list.remove(3);
list.foreach(System.out::println);
}
There is no need to check if i==3, simply remove it before the for loop.
break; instead of continue;
System.out.println(i); if print following elements code is broken.It looks like that loop will be having a different conditional later on as otherwise you can simply do as JoschJava stated.
However if you truly want to iterate through all of your elements and remove a specific one during the loop, you may want to shift the index backwards afterwards. If that is the case, I would add this at the end of your conditional body:
i -= 1;
It isn't safe at all. When you know you might temper the list during iteration, convert your list object into Iterator object then use its methods : hasNext, next, remove...
i, not the element at indexi. Result is that 4th element is removed from list, and that code prints0 1 2 4 5 6 7 8 9, skipping the number3, but not skipping any element.Iteratorimplementation throws aConcurrentModifcationExceptionif you iterate over it and modify the underlying collection.