return classpath == null ? null : classpath.iterator();
    }

    // -------------------------------------------------------------------------------------------
    public ClasspathContainer add(ArtifactMetadata md) {
        if (classpath == null) {
            classpath = new ArrayList<>(16);
        }

        classpath.add(md);

        return this;
    }

@Experimental
@Immutable
public interface ArtifactCoordinates {
    /**
     * {@return the group identifier of the artifact}.
     */
    @Nonnull
    String getGroupId();

    /**
     * {@return the identifier of the artifact}.
     */
    @Nonnull
    String getArtifactId();

    /**
     * Returns the classifier of the artifact.
     *
     * @return the classifier or an empty string if none, never {@code null}
     */

        return null;
    }

    /**
     * Converts a package name to a directory name and returns it.
     *
     * @param packageName
     *            The package name.
     * @return The directory name.
     */
    protected static String toDirectoryName(final String packageName) {
        if (StringUtil.isEmpty(packageName)) {
            return null;
        }

    }
    if (exceptions.size() == 1) {
      Throwable temp = exceptions.iterator().next();
      if (temp instanceof RuntimeException) {
        return (RuntimeException) temp;
      } else {
        return new RuntimeException(temp);
      }
    }
    return new ClusterException(exceptions);
  }

     *
     * @return the unique identifier of type IDTYPE.
     */
    IDTYPE getId();

    /**
     * Sets the unique identifier for the URL queue.
     *
     * @param id the unique identifier to set
     */
    void setId(IDTYPE id);

    /**
     * Retrieves the session ID associated with this URL queue.
     *
     * @return the session ID as a String.
     */

        } catch (InvalidVersionSpecificationException e) {
            return null;
        }

        return artifactFactory.createPluginArtifact(plugin.getGroupId(), plugin.getArtifactId(), versionRange);
    }

    @Override
    public Artifact createProjectArtifact(String groupId, String artifactId, String version) {
        return createArtifact(groupId, artifactId, version, "pom");
    }

    @Override

    return comparator.compare(a, b);
  }

  @Override
  public boolean equals(@Nullable Object object) {
    if (object == this) {
      return true;
    }
    if (object instanceof ComparatorOrdering) {
      ComparatorOrdering<?> that = (ComparatorOrdering<?>) object;
      return this.comparator.equals(that.comparator);
    }
    return false;
  }

  @Override

  }

  /**
   * {@inheritDoc}
   *
   * <p>Creates an empty {@code LinkedHashSet} for a collection of values for one key.
   *
   * @return a new {@code LinkedHashSet} containing a collection of values for one key
   */
  @Override
  Set<V> createCollection() {
    return Platform.newLinkedHashSetWithExpectedSize(valueSetCapacity);
  }

  /**
   * {@inheritDoc}
   *

            if (a.getArtifactId().equals(id) && a.getGroupId().equals(GROUP_ID)) {
                return a;
            }
        }
        return null;
    }

    private ArtifactResolutionResult collect(Set<Artifact> artifacts) throws ArtifactResolutionException {
        return collect(artifacts, null);
    }

   *
   * @param function the function to be used for loading values; must never return {@code null}
   * @return a cache loader that loads values by passing each key to {@code function}
   */
  public static <K, V> CacheLoader<K, V> from(Function<K, V> function) {
    return new FunctionToCacheLoader<>(function);
  }

  /**