ValueGraph (Guava: Google Core Libraries for Java 23.5-jre API)

Type Parameters:

N - Node parameter type

V - Value parameter type

All Known Subinterfaces:

MutableValueGraph<N,V>

All Known Implementing Classes:

AbstractValueGraph, ImmutableValueGraph
```
@Beta
public interface ValueGraph<N,V>
```
An interface for graph-structured data, whose edges have associated non-unique values.
A graph is composed of a set of nodes and a set of edges connecting pairs of nodes.
There are three primary interfaces provided to represent graphs. In order of increasing complexity they are: Graph, ValueGraph, and Network. You should generally prefer the simplest interface that satisfies your use case. See the "Choosing the right graph type" section of the Guava User Guide for more details.
Capabilities

ValueGraph supports the following use cases (definitions of terms):
- directed graphs
- undirected graphs
- graphs that do/don't allow self-loops
- graphs whose nodes/edges are insertion-ordered, sorted, or unordered
- graphs whose edges have associated values
ValueGraph, as a subtype of Graph, explicitly does not support parallel edges, and forbids implementations or extensions with parallel edges. If you need parallel edges, use Network. (You can use a positive Integer edge value as a loose representation of edge multiplicity, but the *degree() and mutation methods will not reflect your interpretation of the edge value as its multiplicity.)
Building a ValueGraph

The implementation classes that common.graph provides are not public, by design. To create an instance of one of the built-in implementations of ValueGraph, use the ValueGraphBuilder class:
```
   MutableValueGraph<Integer, Double> graph = ValueGraphBuilder.directed().build();
 
```
ValueGraphBuilder.build() returns an instance of MutableValueGraph, which is a subtype of ValueGraph that provides methods for adding and removing nodes and edges. If you do not need to mutate a graph (e.g. if you write a method than runs a read-only algorithm on the graph), you should use the non-mutating ValueGraph interface, or an ImmutableValueGraph.
You can create an immutable copy of an existing ValueGraph using ImmutableValueGraph.copyOf(ValueGraph):
```
   ImmutableValueGraph<Integer, Double> immutableGraph = ImmutableValueGraph.copyOf(graph);
 
```
Instances of ImmutableValueGraph do not implement MutableValueGraph (obviously!) and are contractually guaranteed to be unmodifiable and thread-safe.
The Guava User Guide has more information on (and examples of) building graphs.
Additional documentation

See the Guava User Guide for the common.graph package ("Graphs Explained") for additional documentation, including:
Since:

20.0

Author:

James Sexton, Joshua O'Madadhain

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`Set<N>`	`adjacentNodes(N node)` Returns the nodes which have an incident edge in common with `node` in this graph.
`boolean`	`allowsSelfLoops()` Returns true if this graph allows self-loops (edges that connect a node to itself).
`Graph<N>`	`asGraph()` Returns a live view of this graph as a `Graph`.
`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`).
`Set<EndpointPair<N>>`	`edges()` Returns all edges in this graph.
`Optional<V>`	`edgeValue(N nodeU, N nodeV)` Returns the value of the edge connecting `nodeU` to `nodeV`, if one is present; otherwise, returns `Optional.empty()`.
`V`	`edgeValueOrDefault(N nodeU, N nodeV, V defaultValue)` Returns the value of the edge connecting `nodeU` to `nodeV`, if one is present; otherwise, returns `defaultValue`.
`boolean`	`equals(Object object)` Returns `true` iff `object` is a `ValueGraph` that has the same elements and the same structural relationships as those in this graph.
`boolean`	`hasEdgeConnecting(N nodeU, N nodeV)` Returns true if there is an edge directly connecting `nodeU` to `nodeV`.
`int`	`hashCode()` Returns the hash code for this graph.
`int`	`inDegree(N node)` Returns the count of `node`'s incoming edges (equal to `predecessors(node).size()`) in a directed graph.
`boolean`	`isDirected()` Returns true if the edges in this graph are directed.
`ElementOrder<N>`	`nodeOrder()` Returns the order of iteration for the elements of `nodes()`.
`Set<N>`	`nodes()` Returns all nodes in this graph, in the order specified by `nodeOrder()`.
`int`	`outDegree(N node)` Returns the count of `node`'s outgoing edges (equal to `successors(node).size()`) in a directed graph.
`Set<N>`	`predecessors(N node)` Returns all nodes in this graph adjacent to `node` which can be reached by traversing `node`'s incoming edges against the direction (if any) of the edge.
`Set<N>`	`successors(N node)` Returns all nodes in this graph adjacent to `node` which can be reached by traversing `node`'s outgoing edges in the direction (if any) of the edge.

- Method Detail
  - nodes
```
Set<N> nodes()
```
    Returns all nodes in this graph, in the order specified by nodeOrder().
  - edges
```
Set<EndpointPair<N>> edges()
```
    Returns all edges in this graph.
  - asGraph
```
Graph<N> asGraph()
```
    Returns a live view of this graph as a Graph. The resulting Graph will have an edge connecting node A to node B if this ValueGraph has an edge connecting A to B.
  - isDirected
```
boolean isDirected()
```
    Returns true if the edges in this graph are directed. Directed edges connect a source node to a target node, while undirected edges connect a pair of nodes to each other.
  - allowsSelfLoops
```
boolean allowsSelfLoops()
```
    Returns true if this graph allows self-loops (edges that connect a node to itself). Attempting to add a self-loop to a graph that does not allow them will throw an IllegalArgumentException.
  - nodeOrder
```
ElementOrder<N> nodeOrder()
```
    Returns the order of iteration for the elements of nodes().
  - adjacentNodes
```
Set<N> adjacentNodes(N node)
```
    Returns the nodes which have an incident edge in common with node in this graph.
  - predecessors
```
Set<N> predecessors(N node)
```
    Returns all nodes in this graph adjacent to node which can be reached by traversing node's incoming edges against the direction (if any) of the edge.
    In an undirected graph, this is equivalent to adjacentNodes(Object).
  - successors
```
Set<N> successors(N node)
```
    Returns all nodes in this graph adjacent to node which can be reached by traversing node's outgoing edges in the direction (if any) of the edge.
    In an undirected graph, this is equivalent to adjacentNodes(Object).
    This is not the same as "all nodes reachable from node by following outgoing edges". For that functionality, see Graphs.reachableNodes(Graph, Object).
  - degree
```
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 adjacentNodes(node).size() + (1 if node has an incident self-loop, 0 otherwise).
    If the count is greater than Integer.MAX_VALUE, returns Integer.MAX_VALUE.
  - inDegree
```
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
```
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
```
boolean hasEdgeConnecting(N nodeU,
                          N nodeV)
```
    Returns true if there is an edge directly connecting 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).
  - edgeValue
```
Optional<V> edgeValue(N nodeU,
                      N nodeV)
```
    Returns the value of the edge connecting nodeU to nodeV, if one is present; otherwise, returns Optional.empty().
    In an undirected graph, this is equal to edgeValue(nodeV, nodeU).
    
    Throws:
    
    IllegalArgumentException - if nodeU or nodeV is not an element of this graph
    
    Since:
    
    23.0 (since 20.0 with return type V)
  - edgeValueOrDefault
```
@Nullable
V edgeValueOrDefault(N nodeU,
                               N nodeV,
                               @Nullable
                               V defaultValue)
```
    Returns the value of the edge connecting nodeU to nodeV, if one is present; otherwise, returns defaultValue.
    In an undirected graph, this is equal to edgeValueOrDefault(nodeV, nodeU, defaultValue).
    
    Throws:
    
    IllegalArgumentException - if nodeU or nodeV is not an element of this graph
  - equals
```
boolean equals(@Nullable
               Object object)
```
    Returns true iff object is a ValueGraph that has the same elements and the same structural relationships as those in this graph.
    Thus, two value graphs A and B are equal if all of the following are true:
    - A and B have equal directedness.
    - A and B have equal node sets.
    - A and B have equal edge sets.
    - The value of a given edge is the same in both A and B.
    Graph properties besides directedness do not affect equality. For example, two graphs may be considered equal even if one allows self-loops and the other doesn't. Additionally, the order in which nodes or edges are added to the graph, and the order in which they are iterated over, are irrelevant.
    A reference implementation of this is provided by AbstractValueGraph.equals(Object).
    Overrides:
    
    equals in class Object
    
    Parameters:
    
    object - 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
```
int hashCode()
```
    Returns the hash code for this graph. The hash code of a graph is defined as the hash code of a map from each of its edges to the associated edge value.
    A reference implementation of this is provided by AbstractValueGraph.hashCode().
    
    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)

Interface ValueGraph<N,V>

Capabilities

Building a `ValueGraph`

Additional documentation

Method Summary

Method Detail

nodes

edges

asGraph

isDirected

allowsSelfLoops

nodeOrder

adjacentNodes

predecessors

successors

degree

inDegree

outDegree

hasEdgeConnecting

edgeValue

edgeValueOrDefault

equals

hashCode

Interface ValueGraph<N,V>

Capabilities

Building a ValueGraph

Additional documentation

Method Summary

Method Detail

nodes

edges

asGraph

isDirected

allowsSelfLoops

nodeOrder

adjacentNodes

predecessors

successors

degree

inDegree

outDegree

hasEdgeConnecting

edgeValue

edgeValueOrDefault

equals

hashCode

Building a `ValueGraph`