Package org.jgrapht

## Interface Graph<V,​E>

• Type Parameters:
V - the graph vertex type
E - the graph edge type
All Known Subinterfaces:
ListenableGraph<V,​E>
All Known Implementing Classes:
AbstractBaseGraph, AbstractGraph, AsGraphUnion, AsSubgraph, AsSynchronizedGraph, AsUndirectedGraph, AsUnmodifiableGraph, AsUnweightedGraph, AsWeightedGraph, BlockCutpointGraph, DefaultDirectedGraph, DefaultDirectedWeightedGraph, DefaultListenableGraph, DefaultUndirectedGraph, DefaultUndirectedWeightedGraph, DirectedAcyclicGraph, DirectedMultigraph, DirectedPseudograph, DirectedWeightedMultigraph, DirectedWeightedPseudograph, EdgeReversedGraph, GraphDelegator, MaskSubgraph, Multigraph, ParanoidGraph, Pseudograph, SimpleDirectedGraph, SimpleDirectedWeightedGraph, SimpleGraph, SimpleWeightedGraph, WeightedMultigraph, WeightedPseudograph

public interface Graph<V,​E>
The root interface in the graph hierarchy. A mathematical graph-theory graph object G(V,E) contains a set V of vertices and a set  E of edges. Each edge e=(v1,v2) in E connects vertex v1 to vertex v2. for more information about graphs and their related definitions see http://mathworld.wolfram.com/Graph.html.

This library generally follows the terminology found at: http://mathworld.wolfram.com/topics/GraphTheory.html. Implementation of this interface can provide simple-graphs, multigraphs, pseudographs etc. The package org.jgrapht.graph provides a gallery of abstract and concrete graph implementations.

This library works best when vertices represent arbitrary objects and edges represent the relationships between them. Vertex and edge instances may be shared by more than one graph.

Through generics, a graph can be typed to specific classes for vertices V and edges E<T>. Such a graph can contain vertices of type V and all sub-types and Edges of type  E and all sub-types.

For guidelines on vertex and edge classes, see this wiki page.

Author:
Barak Naveh
• ### Field Summary

Fields
Modifier and Type Field Description
static double DEFAULT_EDGE_WEIGHT
The default weight for an edge.
• ### Method Summary

All Methods
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 containsEdge​(V sourceVertex, V targetVertex)
Returns true if and only if this graph contains an edge going from the source vertex to the target vertex.
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.
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 removeAllEdges​(java.util.Collection<? extends E> edges)
Removes all the edges in this graph that are also contained in the specified edge collection.
java.util.Set<E> removeAllEdges​(V sourceVertex, V targetVertex)
Removes all the edges going from the specified source vertex to the specified target vertex, and returns a set of all removed edges.
boolean removeAllVertices​(java.util.Collection<? extends V> vertices)
Removes all the vertices in this graph that are also contained in the specified vertex collection.
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.
default void setEdgeWeight​(V sourceVertex, V targetVertex, double weight)
Assigns a weight to an edge between sourceVertex and targetVertex.
java.util.Set<V> vertexSet()
Returns a set of the vertices contained in this graph.
• ### Field Detail

• #### DEFAULT_EDGE_WEIGHT

static final double DEFAULT_EDGE_WEIGHT
The default weight for an edge.
Constant Field Values
• ### Method Detail

• #### getAllEdges

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.

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

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.

Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
an edge connecting source vertex to target vertex.
• #### getVertexSupplier

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 addVertex(). Users can also create the vertex in user code and then use method 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 addVertex(Object) and addVertex(). In such a case the user must make sure never to add vertices in the graph using method 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 addVertex().

Returns:
the vertex supplier or null if the graph has no such supplier
• #### getEdgeSupplier

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 addEdge(Object, Object). Users can also create the edge in user code and then use method 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 edge supplier null if the graph has no such supplier

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, 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 edge supplier (see 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 getEdgeSupplier() returns null, then this method cannot create edges and throws an UnsupportedOperationException.

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.
Throws:
java.lang.IllegalArgumentException - if source or target vertices are not found in the graph.
java.lang.NullPointerException - if any of the specified vertices is null.
java.lang.UnsupportedOperationException - if the graph was not initialized with an edge supplier
getEdgeSupplier()

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, than 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.

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.
Throws:
java.lang.IllegalArgumentException - if source or target vertices are not found in the graph.
java.lang.ClassCastException - if the specified edge is not assignment compatible with the class of edges produced by the edge factory of this graph.
java.lang.NullPointerException - if any of the specified vertices is  null.
addEdge(Object, Object), getEdgeSupplier()

V addVertex()
Creates a new vertex in this graph and returns it.

This method creates the new vertex v using this graph's vertex supplier (see 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 getVertexSupplier() returns null, then this method cannot create vertices and throws an UnsupportedOperationException.

Care must also be taken when interchanging calls to methods addVertex(Object) and addVertex(). In such a case the user must make sure never to add vertices in the graph using method 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 addVertex().

Returns:
The newly created vertex if added to the graph.
Throws:
java.lang.IllegalArgumentException - if the graph supplier returns a vertex which is already in the graph
java.lang.UnsupportedOperationException - if the graph was not initialized with a vertex supplier
getVertexSupplier()

boolean addVertex​(V v)
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.
Parameters:
v - vertex to be added to this graph.
Returns:
true if this graph did not already contain the specified vertex.
Throws:
java.lang.NullPointerException - if the specified vertex is  null.
• #### containsEdge

boolean containsEdge​(V sourceVertex,
V targetVertex)
Returns true if and only if this graph contains an edge going from the source vertex to the target vertex. In undirected graphs the same result is obtained when source and target are inverted. If any of the specified vertices does not exist in the graph, or if is  null, returns false.
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
true if this graph contains the specified edge.
• #### containsEdge

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.
Parameters:
e - edge whose presence in this graph is to be tested.
Returns:
true if this graph contains the specified edge.
• #### containsVertex

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.
Parameters:
v - vertex whose presence in this graph is to be tested.
Returns:
true if this graph contains the specified vertex.
• #### edgeSet

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.

Returns:
a set of the edges contained in this graph.
• #### degreeOf

int degreeOf​(V vertex)
Returns the degree of the specified vertex.

A degree of a vertex in an undirected graph is the number of edges touching that vertex. Edges with same source and target vertices (self-loops) are counted twice.

In directed graphs this method returns the sum of the "in degree" and the "out degree".

Parameters:
vertex - vertex whose degree is to be calculated.
Returns:
the degree of the specified vertex.
Throws:
java.lang.IllegalArgumentException - if vertex is not found in the graph.
java.lang.NullPointerException - if vertex is null.
• #### edgesOf

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.
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.
Throws:
java.lang.IllegalArgumentException - if vertex is not found in the graph.
java.lang.NullPointerException - if vertex is null.
• #### inDegreeOf

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.

Parameters:
vertex - vertex whose degree is to be calculated.
Returns:
the degree of the specified vertex.
Throws:
java.lang.IllegalArgumentException - if vertex is not found in the graph.
java.lang.NullPointerException - if vertex is null.
• #### incomingEdgesOf

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.

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.
Throws:
java.lang.IllegalArgumentException - if vertex is not found in the graph.
java.lang.NullPointerException - if vertex is null.
• #### outDegreeOf

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.

Parameters:
vertex - vertex whose degree is to be calculated.
Returns:
the degree of the specified vertex.
Throws:
java.lang.IllegalArgumentException - if vertex is not found in the graph.
java.lang.NullPointerException - if vertex is null.
• #### outgoingEdgesOf

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.

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.
Throws:
java.lang.IllegalArgumentException - if vertex is not found in the graph.
java.lang.NullPointerException - if vertex is null.
• #### removeAllEdges

boolean removeAllEdges​(java.util.Collection<? extends E> edges)
Removes all the edges in this graph that are also contained in the specified edge collection. After this call returns, this graph will contain no edges in common with the specified edges. This method will invoke the removeEdge(Object) method.
Parameters:
edges - edges to be removed from this graph.
Returns:
true if this graph changed as a result of the call
Throws:
java.lang.NullPointerException - if the specified edge collection is  null.
removeEdge(Object), containsEdge(Object)
• #### removeAllEdges

java.util.Set<E> removeAllEdges​(V sourceVertex,
V targetVertex)
Removes all the edges going from the specified source vertex to the specified target vertex, and returns a set of all removed edges. Returns null if any of the specified vertices does not exist in the graph. If both vertices exist but no edge is found, returns an empty set. This method will either invoke the removeEdge(Object) method, or the removeEdge(Object, Object) method.
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
the removed edges, or null if either vertex is not part of graph
• #### removeAllVertices

boolean removeAllVertices​(java.util.Collection<? extends V> vertices)
Removes all the vertices in this graph that are also contained in the specified vertex collection. After this call returns, this graph will contain no vertices in common with the specified vertices. This method will invoke the removeVertex(Object) method.
Parameters:
vertices - vertices to be removed from this graph.
Returns:
true if this graph changed as a result of the call
Throws:
java.lang.NullPointerException - if the specified vertex collection is  null.
removeVertex(Object), containsVertex(Object)
• #### removeEdge

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.
Parameters:
sourceVertex - source vertex of the edge.
targetVertex - target vertex of the edge.
Returns:
The removed edge, or null if no edge removed.
• #### removeEdge

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.

Parameters:
e - edge to be removed from this graph, if present.
Returns:
true if and only if the graph contained the specified edge.
• #### removeVertex

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.

Parameters:
v - vertex to be removed from this graph, if present.
Returns:
true if the graph contained the specified vertex; false otherwise.
• #### vertexSet

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.

Returns:
a set view of the vertices contained in this graph.
• #### getEdgeSource

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).
Parameters:
e - edge of interest
Returns:
source vertex
• #### getEdgeTarget

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).
Parameters:
e - edge of interest
Returns:
target vertex
• #### getType

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.
Returns:
the graph type
• #### getEdgeWeight

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

void setEdgeWeight​(E e,
double weight)
Assigns a weight to an edge.
Parameters:
e - edge on which to set weight
weight - new weight for edge
Throws:
java.lang.UnsupportedOperationException - if the graph does not support weights
• #### setEdgeWeight

default void setEdgeWeight​(V sourceVertex,
V targetVertex,
double weight)
Assigns a weight to an edge between sourceVertex and targetVertex. If no edge exists between sourceVertex and targetVertex or either of these vertices is null, a NullPointerException is thrown.

When there exist multiple edges between sourceVertex and targetVertex, consider using setEdgeWeight(Object, double) instead.

Parameters:
sourceVertex - source vertex of the edge
targetVertex - target vertex of the edge
weight - new weight for edge
Throws:
java.lang.UnsupportedOperationException - if the graph does not support weights