*     a provided list is null
   * @since 19.0
   */
  public static <B> List<List<B>> cartesianProduct(List<? extends List<? extends B>> lists) {
    return CartesianList.create(lists);
  }

  /**
   * Returns every possible list that can be formed by choosing one element from each of the given

    assertEquals(asList(1, 4, 7, 8, 9, 10), newArrayList(result));
    assertEquals("[1, 4, 7, 8, 9, 10]", result.toString());
  }

  public void testConcatNullPointerException() {
    List<Integer> list1 = newArrayList(1);
    List<Integer> list2 = newArrayList(4);

    assertThrows(NullPointerException.class, () -> FluentIterable.concat(list1, null, list2));
  }

    List<@Nullable Integer> list1 = Lists.newArrayList();
    List<@Nullable Integer> list2 = Lists.newArrayList(1);
    List<@Nullable Integer> list3 = Lists.newArrayList(1, 1);
    List<@Nullable Integer> list4 = Lists.newArrayList(1, 2);
    List<@Nullable Integer> list5 = Lists.newArrayList(1, null, 2);
    List<@Nullable Integer> list6 = Lists.newArrayList(2);

    List<@Nullable Integer> list1 = Lists.newArrayList();
    List<@Nullable Integer> list2 = Lists.newArrayList(1);
    List<@Nullable Integer> list3 = Lists.newArrayList(1, 1);
    List<@Nullable Integer> list4 = Lists.newArrayList(1, 2);
    List<@Nullable Integer> list5 = Lists.newArrayList(1, null, 2);
    List<@Nullable Integer> list6 = Lists.newArrayList(2);

    assertEquals(asList(1, 4, 7, 8, 9, 10), newArrayList(result));
    assertEquals("[1, 4, 7, 8, 9, 10]", result.toString());
  }

  public void testConcatNullPointerException() {
    List<Integer> list1 = newArrayList(1);
    List<Integer> list2 = newArrayList(4);

    assertThrows(NullPointerException.class, () -> Iterables.concat(list1, null, list2));
  }

  }

  public void testCartesianProduct_unrelatedTypes() {
    List<Integer> x = list(1, 2);
    List<String> y = list("3", "4");

    List<Object> exp1 = list((Object) 1, "3");
    List<Object> exp2 = list((Object) 1, "4");
    List<Object> exp3 = list((Object) 2, "3");
    List<Object> exp4 = list((Object) 2, "4");

    assertThat(Lists.<Object>cartesianProduct(x, y))

  }

  public void testCartesianProduct_unrelatedTypes() {
    List<Integer> x = list(1, 2);
    List<String> y = list("3", "4");

    List<Object> exp1 = list((Object) 1, "3");
    List<Object> exp2 = list((Object) 1, "4");
    List<Object> exp3 = list((Object) 2, "3");
    List<Object> exp4 = list((Object) 2, "4");

    assertThat(Lists.<Object>cartesianProduct(x, y))

      List<String> list = Lists.newArrayList(elements);
      list.add("zzz");
      return ImmutableSortedSet.copyOf(list).headSet("zzy");
    }
  }

  public static class ImmutableSortedSetTailsetGenerator extends TestStringSortedSetGenerator {
    @Override
    protected SortedSet<String> create(String[] elements) {
      List<String> list = Lists.newArrayList(elements);
      list.add("\0");

import static com.google.common.collect.Lists.newArrayList;
import static com.google.common.collect.testing.IteratorFeature.MODIFIABLE;
import static java.util.Collections.emptyList;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

    List<String> list = ImmutableList.of("a", "b", "c");
    assertEquals(Lists.newArrayList("a", "b", "c"), list);
  }

  public void testCreation_fourElements() {
    List<String> list = ImmutableList.of("a", "b", "c", "d");
    assertEquals(Lists.newArrayList("a", "b", "c", "d"), list);
  }

  public void testCreation_fiveElements() {
    List<String> list = ImmutableList.of("a", "b", "c", "d", "e");