*     for the keys
   */
  @CanIgnoreReturnValue
  public @Nullable V erase(@Nullable Object rowKey, @Nullable Object columnKey) {
    Integer rowIndex = rowKeyToIndex.get(rowKey);
    Integer columnIndex = columnKeyToIndex.get(columnKey);
    if (rowIndex == null || columnIndex == null) {
      return null;
    }

  * When annotating existing internal code, use `org.jetbrains.annotations.Contract`, e.g. `@Contract(null -> null; !null -> !null)`.
      When doing so, still annotate nullable parameters and the return type as `@Nullable`.
  * Do not use `@Contract` for public APIs.
  * For polynull public APIs, the solution has to be decided on a case-by-case basis.

Do not remove `null` checks on public API boundaries, even if the annotations (or rather lack of them) suggest this.

            throws GraphConflictResolutionException {
        if (policy == null) {
            throw new GraphConflictResolutionException("no GraphConflictResolutionPolicy injected");
        }

        if (graph == null) {
            return null;
        }

        final MetadataGraphVertex entry = graph.getEntry();
        if (entry == null) {
            return null;
        }

        if (graph.isEmpty()) {

            PluginInfo pluginInfo = extractPluginInfo(artifact);
            if (pluginInfo != null) {
                String key = pluginInfo.groupId;
                if (processedPlugins.get(key) == null) {
                    PluginsMetadata pluginMetadata = plugins.get(key);
                    if (pluginMetadata == null) {
                        pluginMetadata = new PluginsMetadata(pluginInfo, timestamp);

    @Override
    protected Invoker createInvoker(ClassWorld classWorld) {
        return new ResidentMavenInvoker(
                ProtoLookup.builder().addMapping(ClassWorld.class, classWorld).build(), null);
    }

    @Override
    protected Parser createParser() {
        return new MavenParser();
    }

    @Test
    void defaultFs(
            @TempDir(cleanup = CleanupMode.ON_SUCCESS) Path cwd,

import org.codehaus.plexus.util.xml.pull.XmlPullParserException;

/**
 * @deprecated Use MavenStaxReader instead
 */
@Deprecated
public class MavenXpp3ReaderEx extends MavenXpp3Reader {

    public MavenXpp3ReaderEx() {
        this(null);
    }

    public MavenXpp3ReaderEx(ContentTransformer contentTransformer) {
        super(contentTransformer != null ? contentTransformer::transform : null, true);
    }

  public T or(Supplier<? extends T> supplier) {
    return checkNotNull(
        supplier.get(), "use Optional.orNull() instead of a Supplier that returns null");
  }

  @Override
  public @Nullable T orNull() {
    return null;
  }

  @Override
  public Set<T> asSet() {
    return Collections.emptySet();
  }

  @Override
  public <V> Optional<V> transform(Function<? super T, V> function) {
    checkNotNull(function);

      return;
    }
    this.firstEntry = ENDPOINT;
    this.lastEntry = ENDPOINT;
    // Either both arrays are null or neither is, but we check both to satisfy the nullness checker.
    if (predecessor != null && successor != null) {
      Arrays.fill(predecessor, 0, size(), 0);
      Arrays.fill(successor, 0, size(), 0);
    }
    super.clear();
  }

  /*

      return;
    }
    this.firstEntry = ENDPOINT;
    this.lastEntry = ENDPOINT;
    // Either both arrays are null or neither is, but we check both to satisfy the nullness checker.
    if (predecessor != null && successor != null) {
      Arrays.fill(predecessor, 0, size(), 0);
      Arrays.fill(successor, 0, size(), 0);
    }
    super.clear();
  }

  /*

      } catch (Exception ignore) {
        // probably URISyntaxException or IllegalArgumentException
        // fall back to copying URLs to files in the testDir == null block below
      }
    }

    if (testDir == null) {
      // testdata resources aren't file:// urls, so create a directory to store them in and then
      // copy the resources to the filesystem as needed