com.google.common.graph

Class AbstractGraph<N>

java.lang.Object

com.google.common.graph.AbstractGraph<N>

Type Parameters:

N - Node parameter type

All Implemented Interfaces:

Graph<N>

Direct Known Subclasses:

ImmutableGraph

@Beta
public abstract class AbstractGraph<N>
extends Object
implements Graph<N>

This class provides a skeletal implementation of Graph. It is recommended to extend this class rather than implement Graph directly.

Since:

20.0

Author:

James Sexton

Constructor Summary

Constructors

Constructor and Description
AbstractGraph()

Method Summary

Modifier and Type	Method and Description
int	degree(N node) Returns the count of node's incident edges, counting self-loops twice (equivalently, the number of times an edge touches node).
protected long	edgeCount() Returns the number of edges in this graph; used to calculate the size of edges().
Set<EndpointPair<N>>	edges() An implementation of BaseGraph.edges() defined in terms of nodes() and successors(Object).
boolean	equals(@Nullable Object obj) Indicates whether some other object is "equal to" this one.
boolean	hasEdgeConnecting(EndpointPair<N> endpoints) Returns true if there is an edge that directly connects endpoints (in the order, if any, specified by endpoints).
boolean	hasEdgeConnecting(N nodeU, N nodeV) Returns true if there is an edge that directly connects nodeU to nodeV.
int	hashCode() Returns a hash code value for the object.
ElementOrder<N>	incidentEdgeOrder() Returns an ElementOrder that specifies the order of iteration for the elements of edges(), adjacentNodes(Object), predecessors(Object), successors(Object) and incidentEdges(Object).
Set<EndpointPair<N>>	incidentEdges(N node) Returns the edges in this graph whose endpoints include node.
int	inDegree(N node) Returns the count of node's incoming edges (equal to predecessors(node).size()) in a directed graph.
protected boolean	isOrderingCompatible(EndpointPair<?> endpoints)
int	outDegree(N node) Returns the count of node's outgoing edges (equal to successors(node).size()) in a directed graph.
String	toString() Returns a string representation of this graph.
protected void	validateEndpoints(EndpointPair<?> endpoints) Throws IllegalArgumentException if the ordering of endpoints is not compatible with the directionality of this graph.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.google.common.graph.Graph

adjacentNodes, allowsSelfLoops, degree, edges, hasEdgeConnecting, hasEdgeConnecting, incidentEdgeOrder, incidentEdges, inDegree, isDirected, nodeOrder, nodes, outDegree, predecessors, successors

Constructor Detail

AbstractGraph

public AbstractGraph()

Method Detail

equals

public final boolean equals(@Nullable Object obj)

Description copied from class: java.lang.Object

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

• It is reflexive: for any non-null reference value x, x.equals(x) should return true.
• It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
• It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
• It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
• For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Specified by:

equals in interface Graph<N>

Overrides:

equals in class Object

Parameters:

obj - the reference object with which to compare.

Returns:

true if this object is the same as the obj argument; false otherwise.

See Also:

Object.hashCode(), HashMap

hashCode

public final int hashCode()

Description copied from class: java.lang.Object

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

The general contract of hashCode is:

• Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
• It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java™ programming language.)

Specified by:

hashCode in interface Graph<N>

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

toString

public String toString()

Returns a string representation of this graph.

Overrides:

toString in class Object

Returns:

a string representation of the object.

edgeCount

protected long edgeCount()

Returns the number of edges in this graph; used to calculate the size of edges(). This implementation requires O(|N|) time. Classes extending this one may manually keep track of the number of edges as the graph is updated, and override this method for better performance.

edges

public Set<EndpointPair<N>> edges()

An implementation of BaseGraph.edges() defined in terms of nodes() and successors(Object).

incidentEdgeOrder

public ElementOrder<N> incidentEdgeOrder()

Returns an ElementOrder that specifies the order of iteration for the elements of edges(), adjacentNodes(Object), predecessors(Object), successors(Object) and incidentEdges(Object).

incidentEdges

public Set<EndpointPair<N>> incidentEdges(N node)

Returns the edges in this graph whose endpoints include node.

This is equal to the union of incoming and outgoing edges.

degree

public int degree(N node)

Returns the count of node's incident edges, counting self-loops twice (equivalently, the number of times an edge touches node).

For directed graphs, this is equal to inDegree(node) + outDegree(node).

For undirected graphs, this is equal to incidentEdges(node).size() + (number of self-loops incident to node).

If the count is greater than Integer.MAX_VALUE, returns Integer.MAX_VALUE.

inDegree

public int inDegree(N node)

Returns the count of node's incoming edges (equal to predecessors(node).size()) in a directed graph. In an undirected graph, returns the degree(Object).

If the count is greater than Integer.MAX_VALUE, returns Integer.MAX_VALUE.

outDegree

public int outDegree(N node)

Returns the count of node's outgoing edges (equal to successors(node).size()) in a directed graph. In an undirected graph, returns the degree(Object).

If the count is greater than Integer.MAX_VALUE, returns Integer.MAX_VALUE.

hasEdgeConnecting

public boolean hasEdgeConnecting(N nodeU,
                                 N nodeV)

Returns true if there is an edge that directly connects nodeU to nodeV. This is equivalent to nodes().contains(nodeU) && successors(nodeU).contains(nodeV).

In an undirected graph, this is equal to hasEdgeConnecting(nodeV, nodeU).

hasEdgeConnecting

public boolean hasEdgeConnecting(EndpointPair<N> endpoints)

Returns true if there is an edge that directly connects endpoints (in the order, if any, specified by endpoints). This is equivalent to edges().contains(endpoints).

Unlike the other EndpointPair-accepting methods, this method does not throw if the endpoints are unordered; it simply returns false. This is for consistency with the behavior of Collection#contains(Object) (which does not generally throw if the object cannot be present in the collection), and the desire to have this method's behavior be compatible with edges().contains(endpoints).

validateEndpoints

protected final void validateEndpoints(EndpointPair<?> endpoints)

Throws IllegalArgumentException if the ordering of endpoints is not compatible with the directionality of this graph.

isOrderingCompatible

protected final boolean isOrderingCompatible(EndpointPair<?> endpoints)