*/
@GwtCompatible
public final class Iterables {
  private Iterables() {}

  /** Returns an unmodifiable view of {@code iterable}. */
  public static <T extends @Nullable Object> Iterable<T> unmodifiableIterable(
      Iterable<? extends T> iterable) {
    checkNotNull(iterable);
    if (iterable instanceof UnmodifiableIterable || iterable instanceof ImmutableCollection) {

   * this method returns {@code true} if {@code iterable1} and {@code iterable2} contain the same
   * number of elements and every element of {@code iterable1} is equal to the corresponding element
   * of {@code iterable2}.
   */
  public static boolean elementsEqual(Iterable<?> iterable1, Iterable<?> iterable2) {
    if (iterable1 instanceof Collection && iterable2 instanceof Collection) {

  }

  private void testGetOnAbc(Iterable<String> iterable) {
    try {
      Iterables.get(iterable, -1);
      fail();
    } catch (IndexOutOfBoundsException expected) {
    }
    assertEquals("a", Iterables.get(iterable, 0));
    assertEquals("b", Iterables.get(iterable, 1));
    assertEquals("c", Iterables.get(iterable, 2));
    try {
      Iterables.get(iterable, 3);
      fail();

  }

  private void testGetOnAbc(Iterable<String> iterable) {
    try {
      Iterables.get(iterable, -1);
      fail();
    } catch (IndexOutOfBoundsException expected) {
    }
    assertEquals("a", Iterables.get(iterable, 0));
    assertEquals("b", Iterables.get(iterable, 1));
    assertEquals("c", Iterables.get(iterable, 2));
    try {
      Iterables.get(iterable, 3);
      fail();

import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertTrue;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Equivalence;
import com.google.common.collect.Iterables;
import com.google.common.testing.RelationshipTester.Item;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.ArrayList;
import java.util.List;
import org.jspecify.annotations.NullMarked;

  static final Iterable<Double> INFINITIES =
      Doubles.asList(Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY);
  static final Iterable<Double> FINITE_DOUBLE_CANDIDATES;
  static final Iterable<Double> POSITIVE_FINITE_DOUBLE_CANDIDATES;
  static final Iterable<Double> ALL_DOUBLE_CANDIDATES;
  static final Iterable<Double> DOUBLE_CANDIDATES_EXCEPT_NAN;

  static {

      Iterable<? extends T> a,
      Iterable<? extends T> b,
      Iterable<? extends T> c,
      Iterable<? extends T> d) {
    return concatNoDefensiveCopy(a, b, c, d);
  }

  /**
   * Returns a fluent iterable that combines several iterables. The returned iterable has an
   * iterator that traverses the elements of each iterable in {@code inputs}. The input iterators
   * are not polled until necessary.
   *

      Iterable<? extends T> a,
      Iterable<? extends T> b,
      Iterable<? extends T> c,
      Iterable<? extends T> d) {
    return concatNoDefensiveCopy(a, b, c, d);
  }

  /**
   * Returns a fluent iterable that combines several iterables. The returned iterable has an
   * iterator that traverses the elements of each iterable in {@code inputs}. The input iterators
   * are not polled until necessary.
   *

    /**
     * Returns an {@link Iterable} that wraps a {@link MultiIterator} for use in a for-each statement.
     *
     * @param <E> the element type
     * @param iterables the array of {@link Iterable} (must not be {@literal null})
     * @return an {@link Iterable} wrapping a {@link MultiIterator}
     */
    public static <E> Iterable<E> iterable(final Iterable<E>... iterables) {

   */
  private Iterable<List<Object>> buildCartesianProduct(Set<?>... sets) {
    List<Set<Optional<?>>> optionalSets = Lists.newArrayListWithExpectedSize(sets.length);
    for (Set<?> set : sets) {
      Set<Optional<?>> optionalSet =
          Sets.newLinkedHashSet(Iterables.transform(set, NULLABLE_TO_OPTIONAL));
      optionalSets.add(optionalSet);
    }