OldSuperInternal returnTypeOverridenMethod() { return null }
    }

    static class OldBase extends OldSuperInternal {
        void anotherPublicMethod() {}

        OldBase returnTypeOverridenMethod() { return null }
    }

    static class OldSub extends OldBase {
        OldSub returnTypeOverridenMethod() { return null }
    }

    static class NewSuperInternal {}

    }

    @Override
    public String getBaseVersion() {
        if (baseVersion == null && version != null) {
            setBaseVersionInternal(version);
        }

        return baseVersion;
    }

    protected String getBaseVersionInternal() {
        if ((baseVersion == null) && (version != null)) {
            setBaseVersionInternal(version);
        }

        return baseVersion;
    }

        if (!matcher.matches()) {
            return null;
        }

        String className = null;
        if (matcher.group(1).length() > 0) {
            className = typeNameResolver.resolve(matcher.group(1), classMetaData);
            if (className == null) {
                return null;
            }
        }
        if (matcher.group(2) == null) {

   * find it when available. When this is null, use the slow way.
   */
  @J2ktIncompatible @GwtIncompatible // java.lang.reflect
  private static final @Nullable Method getStackTraceElementMethod =
      (jla == null) ? null : getGetMethod();

  /**
   * The "getStackTraceDepth" method, only available on some JDKs so we use reflection to find it
   * when available. When this is null, use the slow way.
   */

     *
     * @param activeProfileIds The identifiers of those profiles to activate, may be {@code null}.
     * @return This context, never {@code null}.
     */
    public DefaultProfileActivationContext setActiveProfileIds(List<String> activeProfileIds) {
        if (activeProfileIds != null) {
            this.activeProfileIds = Collections.unmodifiableList(activeProfileIds);
        } else {

        if (cacheRecord != null && cacheRecord.getException() != null) {
            throw cacheRecord.getException();
        }

        return cacheRecord;
    }

    @Override
    public CacheRecord put(Key key, List<Artifact> pluginArtifacts) {
        Objects.requireNonNull(pluginArtifacts, "pluginArtifacts cannot be null");

        assertUniqueKey(key);

     *            information along, may be <code>null</code>.
     */
    public void merge(Model target, Model source, boolean sourceDominant, Map<?, ?> hints) {
        Objects.requireNonNull(target, "target cannot be null");

        if (source == null) {
            return;
        }

        Map<Object, Object> context = new HashMap<>();
        if (hints != null) {
            context.putAll(hints);
        }

        if (settings.isUsePluginRegistry()) {
            addViolation(problems, Severity.WARNING, "usePluginRegistry", null, "is deprecated and has no effect.");
        }

        List<String> pluginGroups = settings.getPluginGroups();

        if (pluginGroups != null) {
            for (int i = 0; i < pluginGroups.size(); i++) {
                String pluginGroup = pluginGroups.get(i).trim();

                Prerequisites prerequisites =
                        mavenProject.getModel().getDelegate().getPrerequisites();
                if (prerequisites != null && prerequisites.getMaven() != null) {
                    logger.warn(
                            "The project {} uses prerequisites"
                                    + " which is only intended for maven-plugin projects "

  * 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.