* to streams.
 *
 * @author Chris Povirk
 * @author Mike Bostock
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible
public final class Collections2 {
  private Collections2() {}

  /**
   * Returns the elements of {@code unfiltered} that satisfy a predicate. The returned collection is
   * a live view of {@code unfiltered}; changes to one affect the other.
   *

    assertPermutationsCount(1, Collections2.permutations(Collections.<Integer>emptyList()));
    assertPermutationsCount(1, Collections2.permutations(newArrayList(1)));
    assertPermutationsCount(2, Collections2.permutations(newArrayList(1, 2)));
    assertPermutationsCount(6, Collections2.permutations(newArrayList(1, 2, 3)));
    assertPermutationsCount(5040, Collections2.permutations(newArrayList(1, 2, 3, 4, 5, 6, 7)));

    assertPermutationsCount(1, Collections2.permutations(Collections.<Integer>emptyList()));
    assertPermutationsCount(1, Collections2.permutations(newArrayList(1)));
    assertPermutationsCount(2, Collections2.permutations(newArrayList(1, 2)));
    assertPermutationsCount(6, Collections2.permutations(newArrayList(1, 2, 3)));
    assertPermutationsCount(5040, Collections2.permutations(newArrayList(1, 2, 3, 4, 5, 6, 7)));

        return object != null && Collections2.safeContains(delegate, object);
      }

      @Override
      public boolean containsAll(Collection<?> collection) {
        return standardContainsAll(collection);
      }

      @Override
      public boolean remove(@Nullable Object object) {
        return object != null && Collections2.safeRemove(delegate, object);
      }

      @Override

import static java.util.Collections.sort;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.MoreObjects;
import com.google.common.base.Stopwatch;
import com.google.common.collect.Collections2;
import com.google.common.collect.ImmutableCollection;

import static java.util.Collections.sort;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.MoreObjects;
import com.google.common.base.Stopwatch;
import com.google.common.collect.Collections2;
import com.google.common.collect.ImmutableCollection;

    if (iterable1 instanceof Collection && iterable2 instanceof Collection) {
      Collection<?> collection1 = (Collection<?>) iterable1;
      Collection<?> collection2 = (Collection<?>) iterable2;
      if (collection1.size() != collection2.size()) {
        return false;
      }
    }
    return Iterators.elementsEqual(iterable1.iterator(), iterable2.iterator());
  }

  /**

    }
  }

  public void testRemoveAt_exhaustive() {
    int size = reduceExponentIfGwt(8);
    List<Integer> expected = createOrderedList(size);
    for (Collection<Integer> perm : Collections2.permutations(expected)) {
      for (int i = 0; i < perm.size(); i++) {
        MinMaxPriorityQueue<Integer> q = MinMaxPriorityQueue.create(perm);
        q.removeAt(i);
        assertIntactUsingStartedWith(perm, q);

    if (iterable1 instanceof Collection && iterable2 instanceof Collection) {
      Collection<?> collection1 = (Collection<?>) iterable1;
      Collection<?> collection2 = (Collection<?>) iterable2;
      if (collection1.size() != collection2.size()) {
        return false;
      }
    }
    return Iterators.elementsEqual(iterable1.iterator(), iterable2.iterator());
  }

  /**

    public Map<C, V> row(@ParametricNullness R rowKey) {
      return Collections.unmodifiableMap(super.row(rowKey));
    }

    @Override
    public Set<R> rowKeySet() {
      return Collections.unmodifiableSet(super.rowKeySet());
    }

    @Override
    public Map<R, Map<C, V>> rowMap() {
      return unmodifiableMap(Maps.transformValues(super.rowMap(), Collections::unmodifiableMap));
    }

    @Override