previousMetadata.put(remoteRepository, metadata);
            }

            if (repoMetadata.getMetadata() != null) {
                setRepository = repoMetadata.getMetadata().merge(metadata);
            } else {
                repoMetadata.setMetadata(metadata);
                setRepository = true;
            }
        }
        return setRepository;
    }

    /*

      this.mergeFunction = mergeFunction;
    }

    void put(K key, V value) {
      if (map == null) {
        map = new EnumMap<>(singletonMap(key, value));
      } else {
        map.merge(key, value, mergeFunction);
      }
    }

    EnumMapAccumulator<K, V> combine(EnumMapAccumulator<K, V> other) {
      if (this.map == null) {
        return other;
      } else if (other.map == null) {

    }
    try {
      unmod.compute(4, (k, v) -> v);
      fail("UnsupportedOperationException expected");
    } catch (UnsupportedOperationException expected) {
    }
    try {
      unmod.merge(4, "four", (k, v) -> v);
      fail("UnsupportedOperationException expected");
    } catch (UnsupportedOperationException expected) {
    }
    try {
      unmod.clear();

    checkArgument(columnIndex != null, "Column %s not in %s", columnKey, columnList);
    return set(rowIndex, columnIndex, value);
  }

  /*
   * TODO(jlevy): Consider creating a merge() method, similar to putAll() but
   * copying non-null values only.
   */

  /**
   * {@inheritDoc}
   *
   * <p>If {@code table} is an {@code ArrayTable}, its null values will be stored in this table,

        for (ArtifactRepositoryPolicy policy : policies) {
            if (effectivePolicy == null) {
                effectivePolicy = new ArtifactRepositoryPolicy(policy);
            } else {
                effectivePolicy.merge(policy);
            }
        }

        return effectivePolicy;
    }

    public ArtifactRepository createLocalRepository(MavenExecutionRequest request, File localRepository)

  @J2ktIncompatible
  @GwtIncompatible // used only in GwtIncompatible tests
  private interface Merger {

    ListenableFuture<List<String>> merged(ListenableFuture<String> a, ListenableFuture<String> b);

    Merger allMerger =
        new Merger() {
          @Override
          public ListenableFuture<List<String>> merged(
              ListenableFuture<String> a, ListenableFuture<String> b) {

                    PluginExecution existing = merged.get(key);
                    if (existing != null) {
                        element = mergePluginExecution(existing, element, sourceDominant, context);
                    }
                    merged.put(key, element);
                }

                builder.executions(merged.values());
            }
        }

        @Override

import org.apache.maven.api.services.model.*;

/**
 * Handles normalization of a model.
 *
 */
@Named
@Singleton
public class DefaultModelNormalizer implements ModelNormalizer {

    private DuplicateMerger merger = new DuplicateMerger();

    @Override
    public Model mergeDuplicates(Model model, ModelBuilderRequest request, ModelProblemCollector problems) {
        Model.Builder builder = Model.newBuilder(model);

    checkArgument(columnIndex != null, "Column %s not in %s", columnKey, columnList);
    return set(rowIndex, columnIndex, value);
  }

  /*
   * TODO(jlevy): Consider creating a merge() method, similar to putAll() but
   * copying non-null values only.
   */

  /**
   * {@inheritDoc}
   *
   * <p>If {@code table} is an {@code ArrayTable}, its null values will be stored in this table,

    checkNotNull(iterators, "iterators");
    checkNotNull(comparator, "comparator");

    return new MergingIterator<>(iterators, comparator);
  }

  /**
   * An iterator that performs a lazy N-way merge, calculating the next value each time the iterator
   * is polled. This amortizes the sorting cost over the iteration and requires less memory than
   * sorting all elements at once.
   *