org.jscience.computing.graph.graphs
Class Subgraph

java.lang.Object
  extended by org.jscience.computing.graph.graphs.AbstractGraph
      extended by org.jscience.computing.graph.graphs.Subgraph
All Implemented Interfaces:
java.io.Serializable, Graph
Direct Known Subclasses:
DirectedSubgraph, UndirectedSubgraph

public class Subgraph
extends AbstractGraph
implements java.io.Serializable

A subgraph is a graph that has a subset of vertices and a subset of edges with respect to some base graph. More formally, a subgraph G(V,E) that is based on a base graph Gb(Vb,Eb) satisfies the following subgraph property: V is a subset of Vb and E is a subset of Eb. Other than this property, a subgraph is a graph with any respect and fully complies with the Graph interface.

If the base graph is a ListenableGraph, the subgraph listens on the base graph and guarantees the subgraph property. If an edge or a vertex is removed from the base graph, it is automatically removed from the subgraph. Subgraph listeners are informed on such removal only if it results in a cascaded removal from the subgraph. If the subgraph has been created as an induced subgraph it also keeps track of edges being added to its vertices. If vertices are added to the base graph, the subgraph remains unaffected.

If the base graph is not a ListenableGraph, then the subgraph property cannot be guaranteed. If edges or vertices are removed from the base graph, they are not removed from the subgraph.

Modifications to Subgraph are allowed as long as the subgraph property is maintained. Addition of vertices or edges are allowed as long as they also exist in the base graph. Removal of vertices or edges is always allowed. The base graph is never affected by any modification made to the subgraph.

A subgraph may provide a "live-window" on a base graph, so that changes made to its vertices or edges are immediately reflected in the base graph, and vice versa. For that to happen, vertices and edges added to the subgraph must be identical (that is, reference-equal and not only value-equal) to their respective ones in the base graph. Previous versions of this class enforced such identity, at a severe performance cost. Currently it is no longer enforced. If you want to achieve a "live-window" functionality, your safest tactics would be to NOT override the equals()methods of your vertices and edges. If you use a class that has already overridden the equals() method, such as String, than you can use a wrapper around it, or else use it directly but exercise a great care to avoid having different-but-equal instances in the subgraph and the base graph.

This graph implementation guarantees deterministic vertex and edge set ordering (via LinkedHashSet).

Since:
Jul 18, 2003
See Also:
Graph, Set, Serialized Form

Constructor Summary
Subgraph(Graph base, java.util.Set vertexSubset)
          Creates a new induced Subgraph.
Subgraph(Graph base, java.util.Set vertexSubset, java.util.Set edgeSubset)
          Creates a new Subgraph.
 
Method Summary
 boolean addEdge(Edge e)
          Adds the specified edge to this subgraph.
 Edge addEdge(java.lang.Object sourceVertex, java.lang.Object targetVertex)
          Creates a new edge in this graph, going from the source vertex to the target vertex, and returns the created edge.
 boolean addVertex(java.lang.Object v)
          Adds the specified vertex to this subgraph.
 boolean containsEdge(Edge e)
          Returns true if this graph contains the specified edge.
 boolean containsVertex(java.lang.Object v)
          Returns true if this graph contains the specified vertex.
 int degreeOf(java.lang.Object vertex)
           
 java.util.Set edgeSet()
          Returns a set of the edges contained in this graph.
 java.util.List edgesOf(java.lang.Object vertex)
          Returns a list of all edges touching the specified vertex.
 java.util.List getAllEdges(java.lang.Object sourceVertex, java.lang.Object targetVertex)
          Returns a list of all edges connecting source vertex to target vertex if such vertices exist in this graph.
 Edge getEdge(java.lang.Object sourceVertex, java.lang.Object targetVertex)
          Returns an edge connecting source vertex to target vertex if such vertices and such edge exist in this graph.
 EdgeFactory getEdgeFactory()
          Returns the edge factory using which this graph creates new edges.
 java.util.List incomingEdgesOf(java.lang.Object vertex)
           
 int inDegreeOf(java.lang.Object vertex)
           
 boolean isVerifyIntegrity()
          Deprecated. method will be deleted in future versions.
 int outDegreeOf(java.lang.Object vertex)
           
 java.util.List outgoingEdgesOf(java.lang.Object vertex)
           
 boolean removeEdge(Edge e)
          Removes the specified edge from the graph.
 Edge removeEdge(java.lang.Object sourceVertex, java.lang.Object targetVertex)
          Removes an edge going from source vertex to target vertex, if such vertices and such edge exist in this graph.
 boolean removeVertex(java.lang.Object v)
          Removes the specified vertex from this graph including all its touching edges if present.
 void setVerifyIntegrity(boolean verifyIntegrity)
          Deprecated. method will be deleted in future versions. verifyIntegrity flag has no effect now.
 java.util.Set vertexSet()
          Returns a set of the vertices contained in this graph.
 
Methods inherited from class org.jscience.computing.graph.graphs.AbstractGraph
addAllEdges, addAllVertices, assertVertexExist, containsEdge, removeAllEdges, removeAllEdges, removeAllEdges, removeAllVertices, toString, toStringFromSets
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Subgraph

public Subgraph(Graph base,
                java.util.Set vertexSubset,
                java.util.Set edgeSubset)
Creates a new Subgraph.

Parameters:
base - the base (backing) graph on which the subgraph will be based.
vertexSubset - vertices to include in the subgraph. If null then all vertices are included.
edgeSubset - edges to in include in the subgraph. If null then all the edges whose vertices found in the graph are included.

Subgraph

public Subgraph(Graph base,
                java.util.Set vertexSubset)
Creates a new induced Subgraph. The subgraph will keep track of edges being added to its vertex subset as well as deletion of edges and vertices. If base it not listenable, this is identical to the call Subgraph(base, vertexSubset, null) .

Parameters:
base - the base (backing) graph on which the subgraph will be based.
vertexSubset - vertices to include in the subgraph. If null then all vertices are included.
Method Detail

getAllEdges

public java.util.List getAllEdges(java.lang.Object sourceVertex,
                                  java.lang.Object targetVertex)
Description copied from interface: Graph
Returns a list of all edges connecting source vertex to target vertex if such vertices exist in this graph. If any of the vertices does not exist or is null, returns null. If both vertices exist but no edges found, returns an empty list.

In undirected graphs, some of the returned edges may have their source and target vertices in the opposite order. In simple graphs the returned list is either singleton list or empty list.

Specified by:
getAllEdges in interface Graph
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
a list of all edges connecting source vertex to target vertex.
See Also:
Graph.getAllEdges(Object,Object)

getEdge

public Edge getEdge(java.lang.Object sourceVertex,
                    java.lang.Object targetVertex)
Description copied from interface: Graph
Returns an edge connecting source vertex to target vertex if such vertices and such edge exist in this graph. Otherwise returns null. If any of the specified vertices is null returns null

In undirected graphs, the returned edge may have its source and target vertices in the opposite order.

Specified by:
getEdge in interface Graph
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
an edge connecting source vertex to target vertex.
See Also:
Graph.getEdge(Object,Object)

getEdgeFactory

public EdgeFactory getEdgeFactory()
Description copied from interface: Graph
Returns the edge factory using which this graph creates new edges. The edge factory is defined when the graph is constructed and must not be modified.

Specified by:
getEdgeFactory in interface Graph
Returns:
the edge factory using which this graph creates new edges.
See Also:
Graph.getEdgeFactory()

setVerifyIntegrity

public void setVerifyIntegrity(boolean verifyIntegrity)
Deprecated. method will be deleted in future versions. verifyIntegrity flag has no effect now.

Sets the the check integrity flag.

Parameters:
verifyIntegrity -
See Also:
Subgraph

isVerifyIntegrity

public boolean isVerifyIntegrity()
Deprecated. method will be deleted in future versions.

Returns the value of the verifyIntegrity flag.

Returns:
the value of the verifyIntegrity flag.

addEdge

public Edge addEdge(java.lang.Object sourceVertex,
                    java.lang.Object targetVertex)
Description copied from interface: Graph
Creates a new edge in this graph, going from the source vertex to the target vertex, and returns the created edge. Some graphs do not allow edge-multiplicity. In such cases, if the graph already contains an edge from the specified source to the specified target, than this method does not change the graph and returns null.

The source and target vertices must already be contained in this graph. If they are not found in graph IllegalArgumentException is thrown.

This method creates the new edge e using this graph's EdgeFactory. For the new edge to be added e must not be equal to any other edge the graph (even if the graph allows edge-multiplicity). More formally, the graph must not contain any edge e2 such that e2.equals(e). If such e2 is found then the newly created edge e is abandoned, the method leaves this graph unchanged returns null.

Specified by:
addEdge in interface Graph
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
The newly created edge if added to the graph, otherwise null.
See Also:
Graph.addEdge(Object,Object)

addEdge

public boolean addEdge(Edge e)
Adds the specified edge to this subgraph.

Specified by:
addEdge in interface Graph
Parameters:
e - the edge to be added.
Returns:
true if the edge was added, otherwise false.
Throws:
java.lang.NullPointerException
java.lang.IllegalArgumentException
See Also:
Subgraph, Graph.addEdge(Edge)

addVertex

public boolean addVertex(java.lang.Object v)
Adds the specified vertex to this subgraph.

Specified by:
addVertex in interface Graph
Parameters:
v - the vertex to be added.
Returns:
true if the vertex was added, otherwise false.
Throws:
java.lang.NullPointerException
java.lang.IllegalArgumentException
See Also:
Subgraph, Graph.addVertex(Object)

containsEdge

public boolean containsEdge(Edge e)
Description copied from interface: Graph
Returns true if this graph contains the specified edge. More formally, returns true if and only if this graph contains an edge e2 such that e.equals(e2). If the specified edge is null returns false.

Specified by:
containsEdge in interface Graph
Parameters:
e - edge whose presence in this graph is to be tested.
Returns:
true if this graph contains the specified edge.
See Also:
Graph.containsEdge(Edge)

containsVertex

public boolean containsVertex(java.lang.Object v)
Description copied from interface: Graph
Returns true if this graph contains the specified vertex. More formally, returns true if and only if this graph contains a vertex u such that u.equals(v). If the specified vertex is null returns false.

Specified by:
containsVertex in interface Graph
Parameters:
v - vertex whose presence in this graph is to be tested.
Returns:
true if this graph contains the specified vertex.
See Also:
Graph.containsVertex(Object)

degreeOf

public int degreeOf(java.lang.Object vertex)
See Also:
UndirectedGraph.degreeOf(Object)

edgeSet

public java.util.Set edgeSet()
Description copied from interface: Graph
Returns a set of the edges contained in this graph. The set is backed by the graph, so changes to the graph are reflected in the set. If the graph is modified while an iteration over the set is in progress, the results of the iteration are undefined.

The graph implementation may maintain a particular set ordering (e.g. via LinkedHashSet) for deterministic iteration, but this is not required. It is the responsibility of callers who rely on this behavior to only use graph implementations which support it.

Specified by:
edgeSet in interface Graph
Returns:
a set of the edges contained in this graph.
See Also:
Graph.edgeSet()

edgesOf

public java.util.List edgesOf(java.lang.Object vertex)
Description copied from interface: Graph
Returns a list of all edges touching the specified vertex. If no edges are touching the specified vertex returns an empty list.

Specified by:
edgesOf in interface Graph
Parameters:
vertex - the vertex for which a list of touching edges to be returned.
Returns:
a list of all edges touching the specified vertex.
See Also:
Graph.edgesOf(Object)

inDegreeOf

public int inDegreeOf(java.lang.Object vertex)
See Also:
DirectedGraph.inDegreeOf(Object)

incomingEdgesOf

public java.util.List incomingEdgesOf(java.lang.Object vertex)
See Also:
DirectedGraph.incomingEdgesOf(Object)

outDegreeOf

public int outDegreeOf(java.lang.Object vertex)
See Also:
DirectedGraph.outDegreeOf(Object)

outgoingEdgesOf

public java.util.List outgoingEdgesOf(java.lang.Object vertex)
See Also:
DirectedGraph.outgoingEdgesOf(Object)

removeEdge

public boolean removeEdge(Edge e)
Description copied from interface: Graph
Removes the specified edge from the graph. Removes the specified edge from this graph if it is present. More formally, removes an edge e2 such that e2.equals(e), if the graph contains such edge. Returns true if the graph contained the specified edge. (The graph will not contain the specified edge once the call returns).

If the specified edge is null returns false.

Specified by:
removeEdge in interface Graph
Parameters:
e - edge to be removed from this graph, if present.
Returns:
true if and only if the graph contained the specified edge.
See Also:
Graph.removeEdge(Edge)

removeEdge

public Edge removeEdge(java.lang.Object sourceVertex,
                       java.lang.Object targetVertex)
Description copied from interface: Graph
Removes an edge going from source vertex to target vertex, if such vertices and such edge exist in this graph. Returns the edge if removed or null otherwise.

Specified by:
removeEdge in interface Graph
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
The removed edge, or null if no edge removed.
See Also:
Graph.removeEdge(Object,Object)

removeVertex

public boolean removeVertex(java.lang.Object v)
Description copied from interface: Graph
Removes the specified vertex from this graph including all its touching edges if present. More formally, if the graph contains a vertex u such that u.equals(v), the call removes all edges that touch u and then removes u itself. If no such u is found, the call leaves the graph unchanged. Returns true if the graph contained the specified vertex. (The graph will not contain the specified vertex once the call returns).

If the specified vertex is null returns false.

Specified by:
removeVertex in interface Graph
Parameters:
v - vertex to be removed from this graph, if present.
Returns:
true if the graph contained the specified vertex; false otherwise.
See Also:
Graph.removeVertex(Object)

vertexSet

public java.util.Set vertexSet()
Description copied from interface: Graph
Returns a set of the vertices contained in this graph. The set is backed by the graph, so changes to the graph are reflected in the set. If the graph is modified while an iteration over the set is in progress, the results of the iteration are undefined.

The graph implementation may maintain a particular set ordering (e.g. via LinkedHashSet) for deterministic iteration, but this is not required. It is the responsibility of callers who rely on this behavior to only use graph implementations which support it.

Specified by:
vertexSet in interface Graph
Returns:
a set view of the vertices contained in this graph.
See Also:
Graph.vertexSet()