*
     * @param projects The projects to create the dependency graph with
     * @throws DuplicateProjectException
     * @throws CycleDetectedException
     */
    public DefaultProjectDependencyGraph(Collection<MavenProject> projects)
            throws CycleDetectedException, DuplicateProjectException {
        this(projects, projects);
    }

    /**

 * under the License.
 */
package org.apache.maven;

import org.apache.maven.project.CycleDetectedException;

/**
 */
public class ProjectCycleException extends BuildFailureException {
    public ProjectCycleException(String message) {
        super(message);
    }

    public ProjectCycleException(String message, CycleDetectedException cause) {
        super(message, cause);
    }

    }

    void addEdge(Vertex from, Vertex to) throws CycleDetectedException {
        from.children.add(to);
        to.parents.add(from);
        List<String> cycle = findCycle(to);
        if (cycle != null) {
            // remove edge which introduced cycle
            removeEdge(from, to);
            throw new CycleDetectedException(

    synchronized void addEdge(String from, String to) throws CycleDetectedException {
        if (graph.computeIfAbsent(from, l -> new HashSet<>()).add(to)) {
            List<String> cycle = visitCycle(graph, Collections.singleton(to), new HashMap<>(), new LinkedList<>());
            if (cycle != null) {
                // remove edge which introduced cycle
                throw new CycleDetectedException(

import static org.junit.jupiter.api.Assertions.assertThrows;

public class GraphTest {

    @Test
    void testCycle() throws Graph.CycleDetectedException {
        Graph graph = new Graph();
        graph.addEdge("a1", "a2");
        assertThrows(Graph.CycleDetectedException.class, () -> graph.addEdge("a2", "a1"));
    }

    @Test
    public void testPerf() throws IOException {

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.maven.artifact.ArtifactUtils;
import org.apache.maven.plugin.descriptor.PluginDescriptor;
import org.apache.maven.project.CycleDetectedException;
import org.apache.maven.project.DuplicateProjectException;
import org.apache.maven.project.MavenProject;
import org.apache.maven.project.ProjectSorter;

/**
 * ReactorManager - unused
 */
@Deprecated

    private boolean addEdge(Path from, Path p, DefaultModelProblemCollector problems) {
        try {
            dag.addEdge(from.toString(), p.toString());
            return true;
        } catch (Graph.CycleDetectedException e) {
            problems.add(new DefaultModelProblem(
                    "Cycle detected between models at " + from + " and " + p,
                    ModelProblem.Severity.FATAL,
                    null,