org.apache.openjpa.lib.graph.Edge Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.openjpa.lib.graph;
import java.util.List;
/**
* A graph edge. Includes the from and to nodes, an arbitrary user object,
* and a weight. Edges can be either directed or undirected.
*
* @author Abe White
* @since 1.0.0
*/
public class Edge {
/**
* An edge (u, v) is a tree edge if node v was first discovered by
* traversing the edge.
*/
public static final int TYPE_TREE = 1;
/**
* An edge (u, v) is a back edge if it creates a cycle back to an
* ancestor in the graph.
*/
public static final int TYPE_BACK = 2;
/**
* An edge (u, v) is a forward edge if it is not a tree or back edge.
*/
public static final int TYPE_FORWARD = 3;
private final Object _from;
private final Object _to;
private final boolean _directed;
private int _type = 0;
private double _weight = 0;
private Object _userObj = null;
private List _cycle = null;
private boolean _removedFromGraph = false;
/**
* Constructor.
*
* @param from the node the edge comes from
* @param to the node the edge goes to
* @param directed whether the edge is directed
*/
public Edge(Object from, Object to, boolean directed) {
if (from == null)
throw new NullPointerException("from == null");
if (to == null)
throw new NullPointerException("to == null");
_from = from;
_to = to;
_directed = directed;
}
/**
* Constructor.
*
* @param from the node the edge comes from
* @param to the node the edge goes to
* @param directed whether the edge is directed
* @param userObject an associated object
*/
public Edge(Object from, Object to, boolean directed, Object userObject) {
this(from, to, directed);
_userObj = userObject;
}
/**
* Return the node the edge links from.
*/
public Object getFrom() {
return _from;
}
/**
* Return the node the edge links to.
*/
public Object getTo() {
return _to;
}
/**
* Return the node on the opposite end of the given one, or null if the
* given node is not part of this edge.
*/
public Object getOther(Object node) {
if (_to.equals(node))
return _from;
if (_from.equals(node))
return _to;
return null;
}
/**
* Return true if this edge links to the given node. For undirected edges,
* this method returns true if either side is equal to the given node.
*/
public boolean isTo(Object node) {
return _to.equals(node) || (!_directed && _from.equals(node));
}
/**
* Return true if this edge links from the given node. For undirected
* edges, this method returns true if either side is equal to the given
* node.
*/
public boolean isFrom(Object node) {
return _from.equals(node) || (!_directed && _to.equals(node));
}
/**
* Return whether the edge is directed.
*/
public boolean isDirected() {
return _directed;
}
/**
* Return the weight of the edge.
*/
public double getWeight() {
return _weight;
}
/**
* Set the weight of the edge.
*/
public void setWeight(double weight) {
_weight = weight;
}
/**
* Arbitrary user object associated with the edge.
*/
public Object getUserObject() {
return _userObj;
}
/**
* Arbitrary user object associated with the edge.
*/
public void setUserObject(Object obj) {
_userObj = obj;
}
/**
* Traversal bookkeeping info.
*/
public int getType() {
return _type;
}
/**
* Traversal bookkeeping info.
*/
public void setType(int type) {
_type = type;
}
/**
* List of edges forming a cycle. Only set for TYPE_BACK and TYPE_FORWARD
* edges.
*/
public List getCycle() {
return _cycle;
}
/**
* List of edges forming a cycle. Only set for TYPE_BACK and TYPE_FORWARD
* edges.
*/
public void setCycle(List cycle) {
_cycle = cycle;
}
/**
* Returns if this edge is (still) part of the graph.
*/
public boolean isRemovedFromGraph() {
return _removedFromGraph;
}
/**
* Mark this edge as removed from the graph.
*/
public void setRemovedFromGraph() {
this._removedFromGraph = true;
}
/**
* Clear traversal info.
*/
public void clearTraversal() {
_type = 0;
_cycle = null;
}
@Override
public String toString() {
return super.toString() + "[from=" + getFrom() + ";to=" + getTo()
+ ";directed=" + isDirected () + ";weight=" + getWeight () + "]";
}
}