return getCanonicalPath(Optional.ofNullable(
                        ServiceLoader.load(RootLocator.class).iterator().next().findMandatoryRoot(topDirectory))
                .orElseThrow());
    }

        if (coreExtensions.isEmpty() || coreExtensions.get().isEmpty()) {
            return List.of();
        }

        return selectCoreExtensions(
                context, context.invokerRequest.coreExtensions().orElseThrow());
    }

    /**
     * Selects extensions to load discovered from various sources by precedence ("first wins"), as
     * {@link InvokerRequest#coreExtensions()} is in precedence order. Also reports conflicts, if any.

            DispatcherMeta meta = secDispatcher.availableDispatchers().stream()
                    .filter(d -> Objects.equals(config.getDefaultDispatcher(), d.name()))
                    .findFirst()
                    .orElseThrow();
            if (!meta.fields().isEmpty()) {
                dispatcherConfigResult = prompt.prompt(
                        context.header,

        return Optional.ofNullable(plan.get(project)).map(m -> m.get(name));
    }

    public BuildStep requiredStep(MavenProject project, String name) {
        return step(project, name).orElseThrow(() -> new NoSuchElementException("Step " + name + " not found"));
    }

    // add a follow-up plan to this one
    public void then(BuildPlan step) {
        step.plan.forEach((k, v) -> plan.merge(k, v, this::merge));

    private static final class Holder {
        static final XmlService INSTANCE = ServiceLoader.load(XmlService.class)
                .findFirst()
                .orElseThrow(() -> new IllegalStateException("No XmlService implementation found"));

        private Holder() {}
    }

            try (Stream<String> lines = Files.lines(file.toPath())) {
                String packageLine = lines.filter(line -> line.startsWith("package"))
                    .findFirst()
                    .orElseThrow(() -> new IOException("Can't find package definition in file " + file));
                Matcher matcher = pattern.matcher(packageLine);
                if (matcher.find()) {
                    return matcher.group(1);

 *
 * <ul>
 *   <li>This class is serializable; {@code java.util.Optional} is not.
 *   <li>{@code java.util.Optional} has the additional methods {@code ifPresent}, {@code filter},
 *       {@code flatMap}, and {@code orElseThrow}.
 *   <li>{@code java.util} offers the primitive-specialized versions {@code OptionalInt}, {@code
 *       OptionalLong} and {@code OptionalDouble}, the use of which is recommended; Guava does not
 *       have these.
 * </ul>

            MavenProject rootProject = session.getAllProjects().stream()
                    .filter(MavenProject::isExecutionRoot)
                    .findFirst()
                    .orElseThrow(() -> new IllegalStateException("No project in the session is execution root"));

            buildResumptionAnalyzer.determineBuildResumptionData(result).ifPresent(resumption -> {
                try {

    assertThat(response1.body.string()).isEqualTo("ABC")
    val cacheEntry =
      fileSystem.allPaths
        .stream()
        .filter { e: Path -> e.name.endsWith(".0") }
        .findFirst()
        .orElseThrow { NoSuchElementException() }
    corruptCertificate(cacheEntry)
    val response2 = client.newCall(request).execute() // Not Cached!
    assertThat(response2.body.string()).isEqualTo("DEF")