@Override
      protected Multiset<String> create(String[] elements) {
        Multiset<String> multiset = LinkedHashMultiset.create();
        Collections.addAll(multiset, elements);
        multiset.addAll(ELEMENTS_TO_FILTER_OUT);
        return Multisets.filter(multiset, PREDICATE);
      }

      @Override
      public List<String> order(List<String> insertionOrder) {

     * @throws NullPointerException if {@code elements} is null or contains a null element
     */
    @CanIgnoreReturnValue
    @Override
    public Builder<E> addAll(Iterator<? extends E> elements) {
      super.addAll(elements);
      return this;
    }

    @CanIgnoreReturnValue
    Builder<E> combine(Builder<E> builder) {
      checkNotNull(builder);
      add(builder.contents, builder.size);

  public static class ImmutableSortedSetReversedOrderGenerator extends TestStringSetGenerator {

    @Override
    protected SortedSet<String> create(String[] elements) {
      return ImmutableSortedSet.<String>reverseOrder().addAll(asList(elements).iterator()).build();
    }

    @SuppressWarnings("CanIgnoreReturnValueSuggester") // see ImmutableSortedSetExplicitComparator
    @Override
    public List<String> order(List<String> insertionOrder) {

      @Override
      protected Multiset<String> create(String[] elements) {
        Multiset<String> multiset = LinkedHashMultiset.create();
        Collections.addAll(multiset, elements);
        multiset.addAll(ELEMENTS_TO_FILTER_OUT);
        return Multisets.filter(multiset, PREDICATE);
      }

      @Override
      public List<String> order(List<String> insertionOrder) {

    EnumSetAccumulator<E> combine(EnumSetAccumulator<E> other) {
      if (this.set == null) {
        return other;
      } else if (other.set == null) {
        return this;
      } else {
        this.set.addAll(other.set);
        return this;
      }
    }

    ImmutableSet<E> toImmutableSet() {
      if (set == null) {
        return ImmutableSet.of();
      }

     */
    public ToolchainsBuildingException(List<Problem> problems) {
        super(toMessage(problems));

        this.problems = new ArrayList<>();
        if (problems != null) {
            this.problems.addAll(problems);
        }
    }

    /**
     * Gets the problems that caused this exception.
     *
     * @return The problems that caused this exception, never {@code null}.
     */

    }
  }

  public static class BuilderAddAllListGenerator extends TestStringListGenerator {
    @Override
    protected List<String> create(String[] elements) {
      return ImmutableList.<String>builder().addAll(asList(elements)).build();
    }
  }

  public static class BuilderReversedListGenerator extends TestStringListGenerator {
    @Override
    protected List<String> create(String[] elements) {

  @SuppressWarnings("rawtypes") // class literals
  @Override
  protected List<Class<? extends AbstractTester>> getTesters() {
    List<Class<? extends AbstractTester>> testers = copyToList(super.getTesters());
    testers.addAll(ConcurrentMapTestSuiteBuilder.TESTERS);
    return testers;
  }

  @Override
  NavigableMapTestSuiteBuilder<K, V> subSuiteUsing(TestSortedMapGenerator<K, V> generator) {
    return using(generator);
  }

                 * loaded into a dedicated realm which is invisible to plugins (MNG-2749).
                 */
                publicArtifacts.addAll(artifacts);
            }
        }

        if (logger.isDebugEnabled()) {
            logger.debug("Extension realms for project " + model.getId() + ": " + extensionRealms);
        }

        for (O option : options) {
            Optional<List<String>> o = getter.apply(option);
            if (o.isPresent()) {
                had++;
                items.addAll(o.get());
            }
        }
        return had == 0 ? Optional.empty() : Optional.of(List.copyOf(items));
    }

    protected Optional<Map<String, String>> collectMapIfPresentOrEmpty(