code: public static <T> int getDistinctResultCount(int num, Callable<T> callable)
      throws Throwable {
      IdentityHashMap<T, Object> found = new IdentityHashMap<T, Object>();
      Collection<SyncThread<T>> threads = getCompletedThreads(num, callable);
      for (SyncThread<T> s : threads) {
        found.put(s.getResult(), new Object());
      }
      return found.size();
    }
docs: Get the distinct result count for the given callable at the given
  concurrency.
  
  @param <T> the type of the callable
  @param num the concurrency
  @param callable the callable to invoke
  @return the number of distinct (by identity) results found
  @throws Throwable if an exception occurred in one of the invocations