}

    @Override
    public void addSourceRoot(@Nonnull Project project, @Nonnull SourceRoot source) {
        MavenProject prj = getMavenProject(requireNonNull(project, "project" + " cannot be null"));
        prj.addSourceRoot(requireNonNull(source, "source" + " cannot be null"));
    }

    @Override
    public void addSourceRoot(
            @Nonnull Project project,

    //                                                                        ============
    protected void async(final AsyncManager asyncManager, final Runnable runnable) {
        asyncManager.async(new ConcurrentAsyncCall() {
            @Override
            public void callback() {
                runnable.run();
            }

            @Override
            public boolean asPrimary() {

                    PluginManagerException, LifecyclePhaseNotFoundException, LifecycleNotFoundException,
                    PluginVersionResolutionException;

    void execute(MavenSession session);

    // used by the site plugin 3.x
    void calculateForkedExecutions(MojoExecution mojoExecution, MavenSession session)
            throws MojoNotFoundException, PluginNotFoundException, PluginResolutionException,

    /**
     * Name of the property which should be used to override the default download url for the wrapper.
     */
    private static final String PROPERTY_NAME_WRAPPER_URL = "wrapperUrl";

    public static void main(String args[]) {
        System.out.println("- Downloader started");
        File baseDirectory = new File(args[0]);
        System.out.println("- Using base directory: " + baseDirectory.getAbsolutePath());

    }

    public ClassMetaData getOwnerClass() {
        return ownerClass;
    }

    public TypeMetaData getReturnType() {
        return returnType;
    }

    public void setReturnType(TypeMetaData returnType) {
        this.returnType = returnType;
    }

    public MethodMetaData getOverriddenMethod() {
        LinkedList<ClassMetaData> queue = new LinkedList<ClassMetaData>();

     *
     * @param key       The key associated with the extractor. Must not be null or blank.
     * @param extractor The extractor to add. Must not be null.
     */
    public void addExtractor(final String key, final Extractor extractor) {
        if (StringUtil.isBlank(key)) {
            throw new CrawlerSystemException("Extractor key (MIME type) is null or blank. Cannot register extractor without a valid key.");

    private static final Pattern ID_REGEX = Pattern.compile(ID);

    private static final String ILLEGAL_REPO_ID_CHARS = "\\/:\"<>|?*"; // ILLEGAL_FS_CHARS

    @Override
    public void validate(Settings settings, SettingsProblemCollector problems) {
        if (settings.isUsePluginRegistry()) {
            addViolation(problems, Severity.WARNING, "usePluginRegistry", null, "is deprecated and has no effect.");

   * <p>When selecting an executor, note that {@code directExecutor} is dangerous in some cases. See
   * the discussion in the {@link ListenableFuture#addListener ListenableFuture.addListener}
   * documentation.
   */
  public void add(Runnable runnable, Executor executor) {
    // Fail fast on a null. We throw NPE here because the contract of Executor states that it throws
    // NPE on null listener, so we propagate that contract up into the add method as well.

   * very flexible regarding wildcard rules, but this flexibility is not something currently used
   * in practice. To simplify the implementation, we've avoided implementing the flexible rules in
   * favor of supporting what's actually used in practice. That means if these assertions ever fail,
   * the implementation will need to be revisited to support a more flexible rule.
   */

Not all client code is compiled with NullAway.
Do not make a parameter `@Nullable` just to check and throw a `NullPointerException` when it is `null`. 

## Status

ACCEPTED

## Consequences

* Classes are forced to have consistent nullability annotations.
* IDE warnings become more accurate, reducing warnings fatigue.
* Public API nullability annotations become closer to reality.