*/
  @SuppressWarnings("unchecked") // can cast to <T> because non-Ts are removed
  @GwtIncompatible // Class.isInstance
  public static <T> UnmodifiableIterator<T> filter(Iterator<?> unfiltered, Class<T> desiredType) {
    return (UnmodifiableIterator<T>) filter(unfiltered, instanceOf(desiredType));
  }

  /**
   * Returns {@code true} if one or more elements returned by {@code iterator} satisfy the given
   * predicate.
   */

                unfiltered.add("zzz");
                unfiltered.add("abc");
                return Sets.filter(
                    Sets.filter(unfiltered, Collections2Test.LENGTH_1),
                    Collections2Test.NOT_YYY_ZZZ);
              }
            })
        .named("Sets.filter, filtered input")
        .withFeatures(
            CollectionFeature.SUPPORTS_ADD,

                // requireNonNull is safe because the first `size` elements have been filled in.
                requireNonNull(e1);
                requireNonNull(e2);
                return comparator.compare(e1.getKey(), e2.getKey());
              });
          // requireNonNull is safe because the first `size` elements have been filled in.
          Entry<K, V> firstEntry = requireNonNull(entryArray[0]);

    Iterator<String> filtered = Iterators.filter(unfiltered, Predicates.alwaysFalse());
    List<String> expected = Collections.emptyList();
    List<String> actual = Lists.newArrayList(filtered);
    assertEquals(expected, actual);
  }

  public void testFilterMatchAll() {
    Iterator<String> unfiltered = Lists.newArrayList("foo", "bar").iterator();
    Iterator<String> filtered = Iterators.filter(unfiltered, Predicates.alwaysTrue());

 *
 * <p>If the precondition is not met, the {@code Preconditions} method throws an unchecked exception
 * of a specified type, which helps the method in which the exception was thrown communicate that
 * its caller has made a mistake. This allows constructs such as
 *
 * <pre>{@code
 * public static double sqrt(double value) {
 *   if (value < 0) {
 *     throw new IllegalArgumentException("input is negative: " + value);
 *   }

                // requireNonNull is safe because the first `size` elements have been filled in.
                requireNonNull(e1);
                requireNonNull(e2);
                return comparator.compare(e1.getKey(), e2.getKey());
              });
          // requireNonNull is safe because the first `size` elements have been filled in.
          Entry<K, V> firstEntry = requireNonNull(entryArray[0]);

      thrownUnsafeFailure = unsafeFailure;
      // catch absolutely everything and fall through to our 'SafeAtomicHelper'
      // The access control checks that ARFU does means the caller class has to be AbstractFuture
      // instead of SafeAtomicHelper, so we annoyingly define these here
      try {
        helper =
            new SafeAtomicHelper(

   * java.util.stream.Stream#filter}. This method is not being deprecated, but we gently encourage
   * you to migrate to streams.
   */
  // TODO(kevinb): how to omit that last sentence when building GWT javadoc?
  public static <E extends @Nullable Object> Set<E> filter(
      Set<E> unfiltered, Predicate<? super E> predicate) {
    if (unfiltered instanceof SortedSet) {
      return filter((SortedSet<E>) unfiltered, predicate);

   * underlying multimap.
   *
   * <p>The returned multimap isn't threadsafe or serializable, even if {@code unfiltered} is.
   *
   * <p>Many of the filtered multimap's methods, such as {@code size()}, iterate across every
   * key/value mapping in the underlying multimap and determine which satisfy the filter. When a

    Iterator<String> filtered = Iterators.filter(unfiltered, Predicates.alwaysFalse());
    List<String> expected = Collections.emptyList();
    List<String> actual = Lists.newArrayList(filtered);
    assertEquals(expected, actual);
  }

  public void testFilterMatchAll() {
    Iterator<String> unfiltered = Lists.newArrayList("foo", "bar").iterator();
    Iterator<String> filtered = Iterators.filter(unfiltered, Predicates.alwaysTrue());