Remove multiple keys from Map in efficient way?

Question

I have a Map with large number of key values pairs. Now I want to remove selected keys from that Map. Following code shows wha

Answer 1

Just for the sake of completeness:

As guessed java.util.AbstractSet#removeAll really iterates over all entries, but with one little trick: It uses the iterator of the smaller collection:

if (size() <= collection.size()) {
    Iterator it = iterator();
    while (it.hasNext()) {
        if (collection.contains(it.next())) {
            it.remove();
        }
    }
} else {
    Iterator it = collection.iterator();
    while (it.hasNext()) {
        remove(it.next());
    }
}