LinkedList<ScopeState> stack = values.get();
        if (stack == null || stack.isEmpty()) {
            throw new IllegalStateException();
        }
        return stack.getFirst();
    }

    public void exit() throws MojoExecutionException {
        final LinkedList<ScopeState> stack = values.get();
        if (stack == null || stack.isEmpty()) {
            throw new IllegalStateException();
        }

    }

    public Conflict popConflict() {
        assert !conflicts.isEmpty();
        Conflict conflict = conflicts.pop();
        for (K participant : conflict.participants) {
            conflictsByParticipant.remove(participant);
        }
        return conflict;
    }

    public boolean isEmpty() {
        return conflicts.isEmpty();
    }

    boolean hasMatchingConflict(Predicate<T> predicate) {

        if (jdk == null) {
            return false;
        }

        String version = context.getSystemProperties().get("java.version");

        if (version == null || version.isEmpty()) {
            problems.add(
                    BuilderProblem.Severity.ERROR,
                    ModelProblem.Version.BASE,
                    "Failed to determine Java version for profile " + profile.getId(),

        if (jdk == null) {
            return false;
        }

        String version = context.getSystemProperties().get("java.version");

        if (version == null || version.isEmpty()) {
            problems.add(new ModelProblemCollectorRequest(Severity.ERROR, Version.BASE)
                    .setMessage("Failed to determine Java version for profile " + profile.getId())

            Model target,
            List<? extends DependencyManagement> sources,
            ModelBuilderRequest request,
            ModelProblemCollector problems) {
        if (sources != null && !sources.isEmpty()) {
            Map<String, Dependency> dependencies = new LinkedHashMap<>();

            DependencyManagement depMgmt = target.getDependencyManagement();

            if (depMgmt != null) {

     *
     * So {@code (b : c).plus(a) == (a : b : c)}
     */
    @CheckReturnValue
    public abstract PersistentList<T> plus(T element);

    public abstract boolean isEmpty();

    private PersistentList() {}

    private static final PersistentList<Object> NIL = new PersistentList<Object>() {
        @Override
        public void forEach(Consumer<? super Object> consumer) {
        }

    Optional<Object> getOptional() {
      if (extras.isEmpty()) {
        return Optional.ofNullable(element);
      } else {
        throw multiples(false);
      }
    }

    Object getElement() {
      if (element == null) {
        throw new NoSuchElementException();
      } else if (extras.isEmpty()) {
        return element;
      } else {
        throw multiples(false);

        }
    }

    @Override
    public synchronized Throwable getCause() {
        if (hideCause.get()) {
            return null;
        }
        return causes.isEmpty() ? null : causes.get(0);
    }

    @SuppressWarnings("DefaultCharset")
    @Override
    public void printStackTrace(PrintStream printStream) {
        PrintWriter writer = new PrintWriter(printStream);

                if (dependency.getGroupId() == null
                        || dependency.getGroupId().isEmpty()
                        || dependency.getArtifactId() == null
                        || dependency.getArtifactId().isEmpty()
                        || dependency.getVersion() == null
                        || dependency.getVersion().isEmpty()) {
                    // guard against case where best-effort resolution for invalid models is requested

            Model target,
            List<? extends DependencyManagement> sources,
            ModelBuildingRequest request,
            ModelProblemCollector problems) {
        if (sources != null && !sources.isEmpty()) {
            Map<String, Dependency> dependencies = new LinkedHashMap<>();

            DependencyManagement depMgmt = target.getDependencyManagement();

            if (depMgmt != null) {