# Class GraphDelegator<V,​E>

java.lang.Object
org.jgrapht.graph.AbstractGraph<V,​E>
org.jgrapht.graph.GraphDelegator<V,​E>
Type Parameters:
V - the graph vertex type
E - the graph edge type
All Implemented Interfaces:
java.io.Serializable, Graph<V,​E>
Direct Known Subclasses:
AsSynchronizedGraph, AsUndirectedGraph, AsUnmodifiableGraph, AsUnweightedGraph, AsWeightedGraph, DefaultListenableGraph, EdgeReversedGraph, ParanoidGraph

public class GraphDelegator<V,​E>
extends AbstractGraph<V,​E>
implements Graph<V,​E>, java.io.Serializable
A graph backed by the the graph specified at the constructor, which delegates all its methods to the backing graph. Operations on this graph "pass through" to the to the backing graph. Any modification made to this graph or the backing graph is reflected by the other.

This graph does not pass the hashCode and equals operations through to the backing graph, but relies on Object's equals and hashCode methods.

This class is mostly used as a base for extending subclasses. It can also be used in order to override the vertex and edge supplier of a graph.

Author:
Barak Naveh
Serialized Form
• ## Field Summary

### Fields inherited from interface org.jgrapht.Graph

DEFAULT_EDGE_WEIGHT
• ## Constructor Summary

Constructors
Constructor Description
GraphDelegator​(Graph<V,​E> graph)
Constructor
GraphDelegator​(Graph<V,​E> graph, java.util.function.Supplier<V> vertexSupplier, java.util.function.Supplier<E> edgeSupplier)
• ## Method Summary

Modifier and Type Method Description
E addEdge​(V sourceVertex, V targetVertex)
Creates a new edge in this graph, going from the source vertex to the target vertex, and returns the created edge.
boolean addEdge​(V sourceVertex, V targetVertex, E e)
Adds the specified edge to this graph, going from the source vertex to the target vertex.
V addVertex()
Creates a new vertex in this graph and returns it.
boolean addVertex​(V v)
boolean containsEdge​(E e)
Returns true if this graph contains the specified edge.
boolean containsVertex​(V v)
Returns true if this graph contains the specified vertex.
int degreeOf​(V vertex)
Returns the degree of the specified vertex.
java.util.Set<E> edgeSet()
Returns a set of the edges contained in this graph.
java.util.Set<E> edgesOf​(V vertex)
Returns a set of all edges touching the specified vertex.
java.util.Set<E> getAllEdges​(V sourceVertex, V targetVertex)
Returns a set of all edges connecting source vertex to target vertex if such vertices exist in this graph.
protected Graph<V,​E> getDelegate()
Return the backing graph (the delegate).
E getEdge​(V sourceVertex, V targetVertex)
Returns an edge connecting source vertex to target vertex if such vertices and such edge exist in this graph.
V getEdgeSource​(E e)
Returns the source vertex of an edge.
java.util.function.Supplier<E> getEdgeSupplier()
Return the edge supplier that the graph uses whenever it needs to create new edges.
V getEdgeTarget​(E e)
Returns the target vertex of an edge.
double getEdgeWeight​(E e)
Returns the weight assigned to a given edge.
GraphType getType()
Get the graph type.
java.util.function.Supplier<V> getVertexSupplier()
Return the vertex supplier that the graph uses whenever it needs to create new vertices.
java.util.Set<E> incomingEdgesOf​(V vertex)
Returns a set of all edges incoming into the specified vertex.
int inDegreeOf​(V vertex)
Returns the "in degree" of the specified vertex.
int outDegreeOf​(V vertex)
Returns the "out degree" of the specified vertex.
java.util.Set<E> outgoingEdgesOf​(V vertex)
Returns a set of all edges outgoing from the specified vertex.
boolean removeEdge​(E e)
Removes the specified edge from the graph.
E removeEdge​(V sourceVertex, V targetVertex)
Removes an edge going from source vertex to target vertex, if such vertices and such edge exist in this graph.
boolean removeVertex​(V v)
Removes the specified vertex from this graph including all its touching edges if present.
void setEdgeWeight​(E e, double weight)
Assigns a weight to an edge.
java.lang.String toString()
Returns a string of the parenthesized pair (V, E) representing this G=(V,E) graph.
java.util.Set<V> vertexSet()
Returns a set of the vertices contained in this graph.

### Methods inherited from class org.jgrapht.graph.AbstractGraph

assertVertexExist, containsEdge, equals, hashCode, removeAllEdges, removeAllEdges, removeAllEdges, removeAllVertices, toStringFromSets

### Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

### Methods inherited from interface org.jgrapht.Graph

containsEdge, iterables, removeAllEdges, removeAllEdges, removeAllVertices, setEdgeWeight
• ## Constructor Details

• ### GraphDelegator

public GraphDelegator​(Graph<V,​E> graph)
Constructor
Parameters:
graph - the backing graph (the delegate).
• ### GraphDelegator

public GraphDelegator​(Graph<V,​E> graph, java.util.function.Supplier<V> vertexSupplier, java.util.function.Supplier<E> edgeSupplier)
Parameters:
graph - the backing graph (the delegate).
vertexSupplier - vertex supplier for the delegator. Can be null in which case the backing graph vertex supplier will be used.
edgeSupplier - edge supplier for the delegator. Can be null in which case the backing graph edge supplier will be used.
• ## Method Details

• ### getVertexSupplier

public java.util.function.Supplier<V> getVertexSupplier()
Return the vertex supplier that the graph uses whenever it needs to create new vertices.

A graph uses the vertex supplier to create new vertex objects whenever a user calls method Graph.addVertex(). Users can also create the vertex in user code and then use method Graph.addVertex(Object) to add the vertex.

In contrast with the Supplier interface, the vertex supplier has the additional requirement that a new and distinct result is returned every time it is invoked. More specifically for a new vertex to be added in a graph v must not be equal to any other vertex in the graph. More formally, the graph must not contain any vertex v2 such that v2.equals(v).

Care must also be taken when interchanging calls to methods Graph.addVertex(Object) and Graph.addVertex(). In such a case the user must make sure never to add vertices in the graph using method Graph.addVertex(Object), which are going to be returned in the future by the supplied vertex supplier. Such a sequence will result into an IllegalArgumentException when calling method Graph.addVertex().

Returns the delegator's vertex supplier or the backing graph's vertex supplier in case of null.

Specified by:
getVertexSupplier in interface Graph<V,​E>
Returns:
the vertex supplier or null if the graph has no such supplier
• ### getEdgeSupplier

public java.util.function.Supplier<E> getEdgeSupplier()
Return the edge supplier that the graph uses whenever it needs to create new edges.

A graph uses the edge supplier to create new edge objects whenever a user calls method Graph.addEdge(Object, Object). Users can also create the edge in user code and then use method Graph.addEdge(Object, Object, Object) to add the edge.

In contrast with the Supplier interface, the edge supplier has the additional requirement that a new and distinct result is returned every time it is invoked. More specifically for a new edge to be added in a graph e must not be equal to any other edge in the graph (even if the graph allows edge-multiplicity). More formally, the graph must not contain any edge e2 such that e2.equals(e).

Returns the delegator's edge supplier or the backing graph's edge supplier in case of null.

Specified by:
getEdgeSupplier in interface Graph<V,​E>
Returns:
the edge supplier null if the graph has no such supplier
• ### getAllEdges

public java.util.Set<E> getAllEdges​(V sourceVertex, V targetVertex)
Returns a set 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 set.

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

Specified by:
getAllEdges in interface Graph<V,​E>
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
a set of all edges connecting source vertex to target vertex.
• ### getEdge

public E getEdge​(V sourceVertex, V targetVertex)
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<V,​E>
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
an edge connecting source vertex to target vertex.

public E addEdge​(V sourceVertex, V targetVertex)
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, then 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 edge supplier (see Graph.getEdgeSupplier()). 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 and returns null.

If the underlying graph implementation's Graph.getEdgeSupplier() returns null, then this method cannot create edges and throws an UnsupportedOperationException.

Specified by:
addEdge in interface Graph<V,​E>
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.
Graph.getEdgeSupplier()

public boolean addEdge​(V sourceVertex, V targetVertex, E e)
Adds the specified edge to this graph, going from the source vertex to the target vertex. More formally, adds the specified edge,  e, to this graph if this graph contains no edge e2 such that e2.equals(e). If this graph already contains such an edge, the call leaves this graph unchanged and returns false. 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, then this method does not change the graph and returns  false. If the edge was added to the graph, returns  true.

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

Specified by:
addEdge in interface Graph<V,​E>
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
e - edge to be added to this graph.
Returns:
true if this graph did not already contain the specified edge.
Graph.addEdge(Object, Object), Graph.getEdgeSupplier()

Creates a new vertex in this graph and returns it.

This method creates the new vertex v using this graph's vertex supplier (see Graph.getVertexSupplier()). For the new vertex to be added v must not be equal to any other vertex in the graph. More formally, the graph must not contain any vertex v2 such that v2.equals(v). If such  v2 is found then the newly created vertex v is abandoned, the method leaves this graph unchanged and throws an IllegalArgumentException.

If the underlying graph implementation's Graph.getVertexSupplier() returns null, then this method cannot create vertices and throws an UnsupportedOperationException.

Care must also be taken when interchanging calls to methods Graph.addVertex(Object) and Graph.addVertex(). In such a case the user must make sure never to add vertices in the graph using method Graph.addVertex(Object), which are going to be returned in the future by the supplied vertex supplier. Such a sequence will result into an IllegalArgumentException when calling method Graph.addVertex().

Specified by:
addVertex in interface Graph<V,​E>
Returns:
The newly created vertex if added to the graph.
Graph.getVertexSupplier()

Adds the specified vertex to this graph if not already present. More formally, adds the specified vertex, v, to this graph if this graph contains no vertex u such that  u.equals(v). If this graph already contains such vertex, the call leaves this graph unchanged and returns false. In combination with the restriction on constructors, this ensures that graphs never contain duplicate vertices.
Specified by:
addVertex in interface Graph<V,​E>
Parameters:
v - vertex to be added to this graph.
Returns:
true if this graph did not already contain the specified vertex.
• ### containsEdge

public boolean containsEdge​(E e)
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<V,​E>
Parameters:
e - edge whose presence in this graph is to be tested.
Returns:
true if this graph contains the specified edge.
• ### containsVertex

public boolean containsVertex​(V v)
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<V,​E>
Parameters:
v - vertex whose presence in this graph is to be tested.
Returns:
true if this graph contains the specified vertex.
• ### degreeOf

public int degreeOf​(V vertex)
Returns the degree of the specified vertex.
Specified by:
degreeOf in interface Graph<V,​E>
Parameters:
vertex - vertex whose degree is to be calculated
Returns:
the degree of the specified vertex
• ### edgeSet

public java.util.Set<E> edgeSet()
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<V,​E>
Returns:
a set of the edges contained in this graph.
• ### edgesOf

public java.util.Set<E> edgesOf​(V vertex)
Returns a set of all edges touching the specified vertex. If no edges are touching the specified vertex returns an empty set.
Specified by:
edgesOf in interface Graph<V,​E>
Parameters:
vertex - the vertex for which a set of touching edges is to be returned.
Returns:
a set of all edges touching the specified vertex.
• ### inDegreeOf

public int inDegreeOf​(V vertex)
Returns the "in degree" of the specified vertex.

The "in degree" of a vertex in a directed graph is the number of inward directed edges from that vertex. See http://mathworld.wolfram.com/Indegree.html.

In the case of undirected graphs this method returns the number of edges touching the vertex. Edges with same source and target vertices (self-loops) are counted twice.

Specified by:
inDegreeOf in interface Graph<V,​E>
Parameters:
vertex - vertex whose degree is to be calculated.
Returns:
the degree of the specified vertex.
• ### incomingEdgesOf

public java.util.Set<E> incomingEdgesOf​(V vertex)
Returns a set of all edges incoming into the specified vertex.

In the case of undirected graphs this method returns all edges touching the vertex, thus, some of the returned edges may have their source and target vertices in the opposite order.

Specified by:
incomingEdgesOf in interface Graph<V,​E>
Parameters:
vertex - the vertex for which the list of incoming edges to be returned.
Returns:
a set of all edges incoming into the specified vertex.
• ### outDegreeOf

public int outDegreeOf​(V vertex)
Returns the "out degree" of the specified vertex.

The "out degree" of a vertex in a directed graph is the number of outward directed edges from that vertex. See http://mathworld.wolfram.com/Outdegree.html.

In the case of undirected graphs this method returns the number of edges touching the vertex. Edges with same source and target vertices (self-loops) are counted twice.

Specified by:
outDegreeOf in interface Graph<V,​E>
Parameters:
vertex - vertex whose degree is to be calculated.
Returns:
the degree of the specified vertex.
• ### outgoingEdgesOf

public java.util.Set<E> outgoingEdgesOf​(V vertex)
Returns a set of all edges outgoing from the specified vertex.

In the case of undirected graphs this method returns all edges touching the vertex, thus, some of the returned edges may have their source and target vertices in the opposite order.

Specified by:
outgoingEdgesOf in interface Graph<V,​E>
Parameters:
vertex - the vertex for which the list of outgoing edges to be returned.
Returns:
a set of all edges outgoing from the specified vertex.
• ### removeEdge

public boolean removeEdge​(E e)
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<V,​E>
Parameters:
e - edge to be removed from this graph, if present.
Returns:
true if and only if the graph contained the specified edge.
• ### removeEdge

public E removeEdge​(V sourceVertex, V targetVertex)
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<V,​E>
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
The removed edge, or null if no edge removed.
• ### removeVertex

public boolean removeVertex​(V v)
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<V,​E>
Parameters:
v - vertex to be removed from this graph, if present.
Returns:
true if the graph contained the specified vertex; false otherwise.
• ### toString

public java.lang.String toString()
Returns a string of the parenthesized pair (V, E) representing this G=(V,E) graph. 'V' is the string representation of the vertex set, and 'E' is the string representation of the edge set.
Overrides:
toString in class AbstractGraph<V,​E>
Returns:
a string representation of this graph.
• ### vertexSet

public java.util.Set<V> vertexSet()
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<V,​E>
Returns:
a set view of the vertices contained in this graph.
• ### getEdgeSource

public V getEdgeSource​(E e)
Returns the source vertex of an edge. For an undirected graph, source and target are distinguishable designations (but without any mathematical meaning).
Specified by:
getEdgeSource in interface Graph<V,​E>
Parameters:
e - edge of interest
Returns:
source vertex
• ### getEdgeTarget

public V getEdgeTarget​(E e)
Returns the target vertex of an edge. For an undirected graph, source and target are distinguishable designations (but without any mathematical meaning).
Specified by:
getEdgeTarget in interface Graph<V,​E>
Parameters:
e - edge of interest
Returns:
target vertex
• ### getEdgeWeight

public double getEdgeWeight​(E e)
Returns the weight assigned to a given edge. Unweighted graphs return 1.0 (as defined by Graph.DEFAULT_EDGE_WEIGHT), allowing weighted-graph algorithms to apply to them when meaningful.
Specified by:
getEdgeWeight in interface Graph<V,​E>
Parameters:
e - edge of interest
Returns:
edge weight
• ### setEdgeWeight

public void setEdgeWeight​(E e, double weight)
Assigns a weight to an edge.
Specified by:
setEdgeWeight in interface Graph<V,​E>
Parameters:
e - edge on which to set weight
weight - new weight for edge
• ### getType

public GraphType getType()
Get the graph type. The graph type can be used to query for additional metadata such as whether the graph supports directed or undirected edges, self-loops, multiple (parallel) edges, weights, etc.
Specified by:
getType in interface Graph<V,​E>
Returns:
the graph type
• ### getDelegate

protected Graph<V,​E> getDelegate()
Return the backing graph (the delegate).
Returns:
the backing graph (the delegate)