final Function<T, ? extends Iterable<T>> nodeToChildrenFunction) {
    checkNotNull(nodeToChildrenFunction);
    return new TreeTraverser<T>() {
      @Override
      public Iterable<T> children(T root) {
        return nodeToChildrenFunction.apply(root);
      }
    };
  }

  /** Returns the children of the specified node. Must not contain null. */
  public abstract Iterable<T> children(T root);

  /**

  }

  /** @since 12.0 */
  @Override
  @CheckForNull
  public E ceiling(E e) {
    return Iterables.<@Nullable E>getFirst(tailSet(e, true), null);
  }

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  @CheckForNull
  public E higher(E e) {
    return Iterables.<@Nullable E>getFirst(tailSet(e, false), null);
  }

  @Override
  public E first() {

   * is {@code explicitTestNames}.
   */
  @VisibleForTesting
  List<Class<?>> findClassesToTest(
      Iterable<? extends Class<?>> classes, Iterable<String> explicitTestNames) {
    // "a.b.Foo" -> a.b.Foo.class
    TreeMap<String, Class<?>> classMap = Maps.newTreeMap();
    for (Class<?> cls : classes) {
      classMap.put(cls.getName(), cls);

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing.google;

import static com.google.common.collect.Iterables.getOnlyElement;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ADD;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ITERATOR_REMOVE;

  }

  /** @since 12.0 */
  @Override
  @CheckForNull
  public E ceiling(E e) {
    return Iterables.<@Nullable E>getFirst(tailSet(e, true), null);
  }

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  @CheckForNull
  public E higher(E e) {
    return Iterables.<@Nullable E>getFirst(tailSet(e, false), null);
  }

  @Override
  public E first() {

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing.google;

import static com.google.common.collect.Iterables.getOnlyElement;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ADD;
import static com.google.common.collect.testing.features.CollectionFeature.SUPPORTS_ITERATOR_REMOVE;

   *
   * <p><b>Exception:</b> for consistency with separator-based splitters, {@code split("")} does not
   * yield an empty iterable, but an iterable containing {@code ""}. This is the only case in which
   * {@code Iterables.size(split(input))} does not equal {@code IntMath.divide(input.length(),
   * length, CEILING)}. To avoid this behavior, use {@code omitEmptyStrings}.
   *

   *
   * @throws NullPointerException if any element in the input is null
   * @since 21.0
   */
  public static <E extends Comparable<? super E>> ImmutableList<E> sortedCopyOf(
      Iterable<? extends E> elements) {
    Comparable<?>[] array = Iterables.toArray(elements, new Comparable<?>[0]);
    checkElementsNotNull((Object[]) array);
    Arrays.sort(array);
    return asImmutableList(array);
  }

  /**

import static java.util.concurrent.TimeUnit.SECONDS;
import static org.junit.Assert.assertThrows;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;
import com.google.common.testing.NullPointerTester;
import com.google.common.testing.TestLogHandler;

   * NavigableSets inherit the tests for filtered Iterables, Collections, Sets, and SortedSets. The
   * actual implementation tests are further down.
   */

  public abstract static class AbstractFilteredIterableTest<C extends Iterable<Integer>>
      extends TestCase {
    abstract C createUnfiltered(Iterable<Integer> contents);

    abstract C filter(C elements, Predicate<? super Integer> predicate);