Что делает это участок кода? [закрыт]

import java.util.Collection;
import java.util.HashSet;
public class CountableHashSet<E> extends HashSet<E> {
    private int count = 0;
    public CountableHashSet(){}
    public CountableHashSet(int initCap, float loadFactor) {
        super(initCap, loadFactor);
    }
    @Override
    public boolean add(E e) {
        count++;
        return super.add(e);
    }
    @Override
    public boolean addAll(Collection<? extends E> collection) {
        count += collection.size();
        return super.addAll(collection);
    }
    public int getCount() {
        return count;
    }
}
CountableHashSet<String> s = new CountableHashSet<>();
s.addAll(Arrays.asList("Виталик", "Витя", "Максим"));