如何从 ArrayLists 的 ArrayList 中删除 ArrayList？

Question

ArrayList<ArrayList<String>> b = new ArrayList<ArrayList<String>>();

I have an ArrayList like the one above with a bunch of ArrayLists as elements, is there a way to remove one of them by index?

I created a for loop to remove one of the ArrayLists and got an error message that says there are incompatible types.

for(int f = 0; f < longDistanceInput.size(); f++){
     ArrayList<ArrayList<String>> newLongDisinput = longDistanceInput.remove(f);
}

Thanks in advance.

Answer 1

I tried to do something like this and got an error message says incompatible types

for(int f = 0; f<longDistanceInput.size(); f ++){ ArrayList<ArrayList<String>> newLongDisinput = longDistanceInput.remove(f);}

That's because longDistanceInput.remove(f) returns a ArrayList<String> , not a ArrayList<ArrayList<String>> .

Try:

ArrayList<String> newLongDisinput = longDistanceInput.remove(f);

However: be careful removing things while iterating forwards: you will end up removing only half the items in the list, because you skip over the one immediately after the one you remove.

Either iterate in reverse; or just use longDistanceInput.remove(0) instead of remove(f) . But note that removing from anything but the large-index end of an ArrayList is rather inefficient: if possible, just don't remove things from the list until after the loop.