InstrumentedSet.java

public class InstrumentedSet<E> extends ForwardingSet<E> {
     private int addCount = 0;

     public InstrumentedSet(Set<E> s) {
          super(s);
     }

     @Override
     public boolean add(E e) {
          addCount++;
          return super.add(e);
     }

     @Override
     public boolean addAll(Collection<? extends E> c) {
          addCount += c.size();
          return super.addAll(c);
     }

     public int getAddCount() {
          return addCount;
     }
}