/**
   * Executes example.
   *
   * @param args Command line arguments, none required.
   */
  public static void main(String[] args) {
    // Typedefs:
    // ---------
    // G -> GridFactory
    // CI1 -> GridInClosure
    // CO -> GridOutClosure
    // CA -> GridAbsClosure
    // F -> GridFunc

    // Data initialisation.
    Random rand = new Random();

    final int size = 20;

    Collection<Integer> nums = new ArrayList<Integer>(size);

    // Generate list of random integers.
    for (int i = 0; i < size; i++) {
      nums.add(rand.nextInt(size));
    }

    // Print generated list.
    X.println("Generated list:");

    F.forEach(nums, F.<Integer>print("", " "));

    // Retain all elements which value low than half generated list size.
    Collection<Integer> res =
        F.retain(
            nums,
            true,
            new P1<Integer>() {
              @Override
              public boolean apply(Integer i) {
                return i < size / 2;
              }
            });

    // Print result.
    X.println("\nResult list:");

    F.forEach(res, F.<Integer>print("", " "));

    // Retain first half of result list.
    F.retain(res, false, res.size() / 2);

    // Print result.
    X.println("\nResult list:");

    F.forEach(res, F.<Integer>print("", " "));
  }
  /** {@inheritDoc} */
  @Override
  public <T extends GridEvent> Collection<T> localEvents(GridPredicate<T> p) {
    A.notNull(p, "p");

    cleanupQueue();

    return F.retain((Collection<T>) evts, true, p);
  }
  /** @throws Exception Thrown if test failed. */
  public void testA() throws Exception {
    Collection<Integer> set = new GridConcurrentWeakHashSet<>();

    Integer i = 1;

    assert set.add(i);
    assert !set.add(i);

    assert set.contains(i);

    assert set.size() == 1;

    Collection<Integer> c = F.asList(2, 3, 4, 5);

    assert set.addAll(c);
    assert !set.addAll(c);

    assert set.containsAll(c);

    assert set.size() == 1 + c.size();

    assert set.remove(i);
    assert !set.remove(i);

    assert !set.contains(i);

    assert set.size() == c.size();

    assert set.removeAll(c);
    assert !set.removeAll(c);

    assert !set.containsAll(c);

    assert set.isEmpty();

    Collection<Integer> c1 = Arrays.asList(1, 3, 5, 7, 9);

    int cnt = 0;

    for (Iterator<Integer> iter = set.iterator(); iter.hasNext(); cnt++) c1.contains(iter.next());

    assert set.size() == cnt;

    assert set.size() == set.toArray().length;

    assert set.addAll(c1);

    assert set.retainAll(c);
    assert !set.retainAll(c);

    Collection<Integer> c2 = F.retain(c1, true, c);

    assert set.containsAll(c2);
    assert !set.containsAll(c1);
    assert !set.containsAll(c);

    assert set.size() == c2.size();

    set.clear();

    assert set.isEmpty();

    try {
      set.iterator().next();

      assert false;
    } catch (NoSuchElementException ignored) {
      assert true;
    }

    try {
      set.add(null);

      assert false;
    } catch (NullPointerException ignored) {
      assert true;
    }
  }