BrokenInstrumentedSet.java

// Broken - Inappropriate use of inheritance!
public class InstrumentedHashSet<E> extends HashSet<E> {
     // The number of attempted element insertions
     private int addCount = 0;
     public InstrumentedHashSet() {
     }
     public InstrumentedHashSet(int initCap, float loadFactor) {
          super(initCap, loadFactor);
     }
     @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;
     }
}