List<@Nullable String> list = newArrayList("a", null, "b", null, "a", null);
    assertEquals(2, frequency(list.iterator(), "a"));
    assertEquals(1, frequency(list.iterator(), "b"));
    assertEquals(0, frequency(list.iterator(), "c"));
    assertEquals(0, frequency(list.iterator(), 4.2));
    assertEquals(3, frequency(list.iterator(), null));
  }

  @GwtIncompatible // slow (~4s)

  // The comparator used by this map.  It's the same as that of sortedDelegate,
  // except that when sortedDelegate's comparator is null, it points to a
  // non-null instance of Ordering.natural().
  // (cpovirk: Is sortedDelegate's comparator really ever null?)
  // The comparator will likely also differ because of our nullAccepting hack.
  // See the bottom of the file for more information about it.

            assertNotNull(lockRequest);
        }

        @Test
        @DisplayName("Should accept null file ID in constructor")
        void testConstructorWithNullFileId() {
            assertDoesNotThrow(() -> new Smb2LockRequest(mockConfig, null, testLocks));
        }

        @Test
        @DisplayName("Should accept empty file ID in constructor")

        encPart.add(new DERTaggedObject(true, 2, new DEROctetString(encryptedData)));
        v.add(new DERTaggedObject(true, 3, new DERSequence(encPart)));

        if (unknownTag != null) {
            v.add(new DERTaggedObject(true, unknownTag, new DERGeneralString("unknown")));
        }

        return new DERSequence(v).getEncoded();
    }

    /**

                    String name =
                            b.getOriginalKey() != null && b.getOriginalKey().getQualifier() instanceof String s
                                    ? s
                                    : "";
                    map.compute(name, (n, ob) -> ob == null || comparator.compare(ob, b) < 0 ? b : ob);
                }

            if (actionResponse == null) {
                throw responseManager.new400("Unsupported request type.");
            }
            return actionResponse;
        } catch (final SsoMessageException e) {
            if (e.getCause() == null) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Metadata response.", e);

		"00000000-0000-0000-0000-0000000000f1",
		"00000000-0000-0000-0000-0000000000f2",
	}
	// Simulate overwrite of null version
	newtierfi := tierfi
	newtierfi.SetTierFreeVersionID(fvIDs[0])
	fatalErr(xl.AddFreeVersion(newtierfi))
	report()
	fatalErr(xl.AddVersion(newtierfi))
	report()

	// Simulate removal of null version
	newtierfi.TransitionTier = ""
	newtierfi.TransitionedObjName = ""
	newtierfi.TransitionStatus = ""

    static ArtifactInstallerRequest build(Session session, Collection<ProducedArtifact> artifacts) {
        return builder()
                .session(requireNonNull(session, "session cannot be null"))
                .artifacts(requireNonNull(artifacts, "artifacts cannot be null"))
                .build();
    }

    @NotThreadSafe
    class ArtifactInstallerRequestBuilder {
        Session session;
        RequestTrace trace;

    /**
     * <b>Warning</b>: ignored (always return <code>null</code>).
     */
    @Override
    public Logger getChildLogger(String name) {
        return null;
    }

    @Override
    public String getName() {
        return logger.getName();
    }

    private void setMdc() {
        if (projectId != null && ProjectBuildLogAppender.getProjectId() == null) {

@Experimental
public class ModelTransformerException extends MavenException {

    public ModelTransformerException() {
        this(null, null);
    }

    public ModelTransformerException(String message) {
        this(message, null);
    }

    public ModelTransformerException(Throwable cause) {
        this(null, cause);
    }

    public ModelTransformerException(String message, Throwable cause) {
        super(message, cause);