}
        }
    }

    @Override
    public List<MavenProject> getUpstreamProjects(MavenProject project, boolean transitive) {
        Objects.requireNonNull(project, "project cannot be null");

        Set<String> projectIds = new HashSet<>();

        getUpstreamProjects(ProjectSorter.getId(project), projectIds, transitive);

        return getSortedProjects(projectIds);
    }

        Set<MavenProject> result = new LinkedHashSet<>();
        for (ProjectSegment projectBuild : projectBuilds) {
            if (projectDependencyGraph
                    .getUpstreamProjects(projectBuild.getProject(), false)
                    .isEmpty()) {
                result.add(projectBuild.getProject());
            }
        }
        if (result.isEmpty() && !projectBuilds.isEmpty()) {

            cache.put(key, list);
        }
        return list;
    }

    @Override
    public List<MavenProject> getUpstreamProjects(MavenProject project, boolean transitive) {
        Key key = new Key(project, transitive, true);
        // Do not use computeIfAbsent here, as the computation is recursive

     *            upstream projects.
     * @return The upstream projects in the build order, never {@code null}.
     */
    List<MavenProject> getUpstreamProjects(MavenProject project, boolean transitive);

        final ProjectDependencyGraph dependencyGraph = getSession().getProjectDependencyGraph();
        nonTransitiveUpstreamProjects = dependencyGraph.getUpstreamProjects(getProject(), false);
        transitiveUpstreamProjects = dependencyGraph.getUpstreamProjects(getProject(), true);
    }

    public MavenSession getSession() {
        return session;
    }

    public MavenProject getProject() {

            Set<MavenProject> projectsSet = new HashSet<>(projects);

            for (MavenProject project : projects) {
                if (makeUpstream) {
                    projectsSet.addAll(graph.getUpstreamProjects(project, true));
                }
                if (makeDownstream) {
                    projectsSet.addAll(graph.getDownstreamProjects(project, true));
                }
            }

            Map<MavenProject, List<MavenProject>> allProjects = new LinkedHashMap<>();
            dependencyGraph
                    .getSortedProjects()
                    .forEach(p -> allProjects.put(p, dependencyGraph.getUpstreamProjects(p, false)));

            BuildPlan plan = new BuildPlan(allProjects);
            for (TaskSegment taskSegment : taskSegments) {