Question

In Java, I would like to use the clear() method on a list so that the items cleared from the sublist are also removed from the original list. Is there a way to create a sublist where the indices are non continuous, so that I can still use the clear() method to remove the items from the original list?

Answer 1

None of the default List implementations support this behavior. You could override ArrayList and support a clear(), remove(), etc.. that turns around and calls remove() on the parent list.

Something like the following example code. But to keep it properly in sync with the parent is going to take a lot of work. If you can limit the number of calls that you need to support then it would be a lot easier of course.

public class SubArrayList<T> extends ArrayList<T> {
    public SubArrayList(List<T> parentList, int start, int end) {
        ...;
    }

    @Override
    public T remove(int index) {
        T removed = super.remove(index);
        // should not remove by position because position in parent might change
        parentList.remove(removed);
        return removed;
    }

    @Override
    public T remove(Object obj) {
        if (super.remove(obj)) {
            parentList.remove(obj);
        }
    }
}