ms.add("b");
    ms.add(null);
    ms.add("a");
    ms.add("b");
    ms.add(null, 2);

    assertThat(ms).containsExactly(null, null, null, "a", "b", "b").inOrder();
    assertEquals(3, ms.count(null));

    SortedSet<@Nullable String> elementSet = ms.elementSet();
    assertEquals(null, elementSet.first());
    assertEquals("b", elementSet.last());

                final String filename = entry.getName();
                final String mimeType = mimeTypeHelper.getContentType(null, filename);
                if (mimeType != null) {
                    final Extractor extractor = extractorFactory.getExtractor(mimeType);
                    if (extractor != null) {
                        try {
                            final Map<String, String> map = new HashMap<>();

     * value is undefined.
     *
     * @return The location of the problem, never {@code null}.
     */
    String getLocation();

    /**
     * Gets the exception that caused this problem (if any).
     *
     * @return The exception that caused this problem or {@code null} if not applicable.
     */
    Exception getException();

    /**
     * Gets the message that describes this problem.

        Metadata repoMetadata = metadata.getMetadata();
        String version = null;
        if (repoMetadata != null && repoMetadata.getVersioning() != null) {
            version = constructVersion(repoMetadata.getVersioning(), artifact.getBaseVersion());
        }

        if (version == null) {
            // use the local copy, or if it doesn't exist - go to the remote repo for it

                    final String fileName = getName(objectKey);
                    final ZonedDateTime lastModified =
                            s3Object.lastModified() != null ? s3Object.lastModified().atZone(java.time.ZoneId.systemDefault()) : null;
                    items.add(new StorageItem(fileName, prefix, false, s3Object.size(), lastModified, encodeId(objectKey)));
                }
            }

     * allowing the CAS below to succeed.
     */
    Thread currentThread = Thread.currentThread();
    if (!compareAndSet(null, currentThread)) {
      return; // someone else has run or is running.
    }

    boolean run = !isDone();
    T result = null;
    Throwable error = null;
    try {
      if (run) {
        result = runInterruptibly();

    protected void finalize() throws Throwable {
        try {
            // Add null check to prevent NPE if object was not fully constructed
            if (this.usageCount != null && this.usageCount.get() != 0) {
                log.warn("Tree handle was not properly released, performing emergency cleanup: "
                        + (this.resourceLoc != null ? this.resourceLoc.getURL() : "unknown"));
                emergencyReleaseHandle();

        if (context.parserRequest.mavenHome() != null) {
            Path result = getCanonicalPath(context.parserRequest.mavenHome());
            context.systemPropertiesOverrides.put(Constants.MAVEN_HOME, result.toString());
            return result;
        } else {
            String mavenHome = System.getProperty(Constants.MAVEN_HOME);
            if (mavenHome == null) {
                throw new IllegalStateException(

  private static final Iterable<@Nullable Integer> iterableNull = Arrays.asList((Integer) null);
  private static final Iterable<@Nullable Integer> iterableNullNull =
      Arrays.asList((Integer) null, null);
  private static final Iterable<@Nullable Integer> iterableNull1 = Arrays.asList(null, 1);
  private static final Iterable<@Nullable Integer> iterable1Null = Arrays.asList(1, null);

    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().removeAll(null) doesn't throws NPE.
    }
  }

  @Override
  public void testEntrySetRetainAllNullFromEmpty() {
    try {
      super.testEntrySetRetainAllNullFromEmpty();
    } catch (RuntimeException tolerated) {
      // GWT's TreeMap.entrySet().retainAll(null) doesn't throws NPE.
    }
  }

  @Override