* {@link TreeSet} or the {@link Map#keySet} of an {@code IdentityHashMap}.
   */
  public static <E extends @Nullable Object> SetView<E> union(
      final Set<? extends E> set1, final Set<? extends E> set2) {
    checkNotNull(set1, "set1");
    checkNotNull(set2, "set2");

    return new SetView<E>() {
      @Override
      public int size() {
        int size = set1.size();

	for {
		select {
		case <-ctx.Done():
			return
		case <-timer.C:
			var wg sync.WaitGroup
			for _, set := range s.sets {
				wg.Add(1)
				go func(set *erasureObjects) {
					defer wg.Done()
					if set == nil {
						return
					}
					set.cleanupDeletedObjects(ctx)
				}(set)
			}
			wg.Wait()

			// Reset for the next interval
			timer.Reset(globalAPIConfig.getDeleteCleanupInterval())

                  protected Set<String> create(String[] elements) {
                    Set<String> set = newHashSet(elements);
                    Set<String> other = newHashSet("wz", "xq");
                    set.addAll(other);
                    other.add("pq");
                    return Sets.difference(set, other);
                  }
                })
            .named("set - set")
            .withFeatures(

                  @Override
                  protected Set<String> create(String[] elements) {
                    Set<String> set1 = newHashSet(elements);
                    set1.add(samples().e3());
                    Set<String> set2 = newHashSet(elements);
                    set2.add(samples().e4());
                    return Sets.intersection(set1, set2);
                  }
                })

    assertTrue(set.containsAll(Sets.newTreeSet(asList("a", "b", "f"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("z"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("b", "d"))));
    assertFalse(set.containsAll(Sets.newTreeSet(asList("f", "d", "a"))));
  }

     *
     * @return The source of the POM or {@code null} if not set.
     */
    ModelSource getModelSource();

    /**
     * Sets the source of the POM to process. Eventually, either {@link #setModelSource(ModelSource)} or
     * {@link #setPomPath(Path)} must be set.
     *
     * @param modelSource The source of the POM to process, may be {@code null}.
     * @return This request, never {@code null}.
     */

                  protected Set<String> create(String[] elements) {
                    Set<String> set = newHashSet(elements);
                    Set<String> other = newHashSet("wz", "xq");
                    set.addAll(other);
                    other.add("pq");
                    return Sets.difference(set, other);
                  }
                })
            .named("set - set")
            .withFeatures(

      if (set.isEmpty()) {
        /*
         * The (tooLow + 1, tooHigh) arguments below would be invalid because tooLow would be
         * greater than tooHigh.
         */
        return ContiguousSet.create(Range.openClosed(0, 1), DiscreteDomain.integers()).subSet(0, 1);
      }
      int tooHigh = set.last() + 1;
      int tooLow = set.first() - 1;
      set.add(tooHigh);

    /**
     * Gets the global settings file.
     *
     * @return The global settings file or {@code null} if none.
     */
    File getGlobalSettingsFile();

    /**
     * Sets the global settings file. A non-existent settings file is equivalent to empty settings. If both user
     * settings and global settings are given, the user settings take precedence.
     *

 */

package com.google.common.collect;

import static com.google.common.collect.Sets.newHashSet;

import com.google.common.base.Predicate;
import com.google.common.collect.FilteredCollectionsTestUtil.AbstractFilteredSetTest;
import java.util.Set;

public final class SetsFilterHashSetTest extends AbstractFilteredSetTest<Set<Integer>> {
  @Override
  Set<Integer> createUnfiltered(Iterable<Integer> contents) {
    return newHashSet(contents);