com.jn.langx.util.collection.graph.DAG Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of langx-java Show documentation

Java lang extensions for java6+, a supplement to , replacement of a Guava, commons-lang. Core utilities, Collection utilities, IO utilities, Cache, Configuration library ...

There is a newer version: 4.8.2

Show newest version

package com.jn.langx.util.collection.graph;

import java.util.List;

public class DAG extends Graph {
    public boolean addEdge(Vertex from, Vertex to, int weight) {
        if (!hasVertex(from.getName())) {
            addVertex(from);
        }
        if (!hasVertex(to.getName())) {
            addVertex(to);
        }
        Edge e = new Edge(from, to, weight);
        if (from.findEdge(to) != null) {
            // 已有该 edge，则不再添加
            return false;
        } else {
            from.addEdge(e);
            to.addEdge(e);
            final List cycle = Graphs.detectCycle(to);

            if (cycle != null) {
                // remove edge which introduced cycle
                removeEdge(from, to);
                final String msg = "Edge between '" + from + "' and '" + to + "' introduces to cycle in the graph";
                throw new CycleDetectedException(msg, cycle);
            }
            edges.add(e);
            return true;
        }
    }
}