java.lang.Object
- it.unimi.dsi.big.webgraph.ImmutableGraph
- - it.unimi.dsi.big.webgraph.labelling.ArcLabelledImmutableGraph
  - - it.unimi.dsi.big.webgraph.labelling.UnionArcLabelledImmutableGraph

All Implemented Interfaces:

it.unimi.dsi.lang.FlyweightPrototype<ImmutableGraph>
```
public class UnionArcLabelledImmutableGraph
extends ArcLabelledImmutableGraph
```
An arc-labelled immutable graph representing the union of two given such graphs. Here by “union” we mean that an arc will belong to the union iff it belongs to at least one of the two graphs (the number of nodes of the union is taken to be the maximum among the number of nodes of each graph). Labels are assumed to have the same prototype in both graphs, and are treated as follows: if an arc is present in but one graph, its label in the resulting graph is going to be the label of the arc in the graph where it comes from; if an arc is present in both graphs, the labels are combined using a provided LabelMergeStrategy.
Remarks about the implementation

Due to the lack of multiple inheritance, we could not extend both UnionImmutableGraph and ArcLabelledImmutableGraph, hence we forcedly decided to extend the latter. The possibility of using delegation on the former was also discarded because the code for reading and merging labels is so tightly coupled with the rest that it would have been essentially useless (and even dangerous) to delegate the iteration methods. As a result, some of the code of this class is actually almost a duplicate of the code of UnionImmutableGraph.

Nested Class Summary
- Nested classes/interfaces inherited from class it.unimi.dsi.big.webgraph.ImmutableGraph
  ImmutableGraph.LoadMethod

Field Summary
- Fields inherited from class it.unimi.dsi.big.webgraph.labelling.ArcLabelledImmutableGraph
  UNDERLYINGGRAPH_PROPERTY_KEY, UNDERLYINGGRAPH_SUFFIX
- Fields inherited from class it.unimi.dsi.big.webgraph.ImmutableGraph
  GRAPHCLASS_PROPERTY_KEY, NUMBER_OF_THREADS_PROPERTY, PROPERTIES_EXTENSION

Constructor Summary

Constructors
Constructor	Description
`UnionArcLabelledImmutableGraph(ArcLabelledImmutableGraph g0, ArcLabelledImmutableGraph g1, LabelMergeStrategy labelMergeStrategy)`	Creates the union of two given graphs.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`UnionArcLabelledImmutableGraph`	`copy()`	Returns a flyweight copy of this immutable graph.
`boolean`	`hasCopiableIterators()`	Whether the node iterators returned by this graph support `NodeIterator.copy(long)`.
`Label[][]`	`labelBigArray(long x)`	Returns a reference to an array containing the labels of the arcs going out of a given node in the same order as the order in which the corresponding successors are returned by `ArcLabelledImmutableGraph.successors(long)`.
`ArcLabelledNodeIterator`	`nodeIterator(long from)`	Returns a node iterator for scanning the graph sequentially, starting from the given node.
`long`	`numNodes()`	Returns the number of nodes of this graph.
`long`	`outdegree(long x)`	Returns the outdegree of a node.
`Label`	`prototype()`	Returns a prototype of the labels used by this graph.
`boolean`	`randomAccess()`	Checks whether this graph provides random access to successor lists.
`long[][]`	`successorBigArray(long x)`	Returns a reference to a big array containing the successors of a given node.
`ArcLabelledNodeIterator.LabelledArcIterator`	`successors(long x)`	Returns a lazy iterator over the successors of a given node.

Methods inherited from class it.unimi.dsi.big.webgraph.labelling.ArcLabelledImmutableGraph
equals, load, load, loadOffline, loadOffline, loadOnce, loadSequential, loadSequential, nodeIterator, toString

Methods inherited from class it.unimi.dsi.big.webgraph.ImmutableGraph
basename, hashCode, intNumNodes, load, loadMapped, loadMapped, numArcs, outdegrees, splitNodeIterators, store, store, wrap, wrap

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - UnionArcLabelledImmutableGraph
```
public UnionArcLabelledImmutableGraph(ArcLabelledImmutableGraph g0,
                                      ArcLabelledImmutableGraph g1,
                                      LabelMergeStrategy labelMergeStrategy)
```
    Creates the union of two given graphs.
    
    Parameters:
    
    g0 - the first graph.
    
    g1 - the second graph.
    
    labelMergeStrategy - the strategy used to merge labels when the same arc is present in both graphs.
- Method Detail
  - copy
```
public UnionArcLabelledImmutableGraph copy()
```
    Description copied from class: ImmutableGraph
    
    Returns a flyweight copy of this immutable graph.
    
    Specified by:
    
    copy in interface it.unimi.dsi.lang.FlyweightPrototype<ImmutableGraph>
    
    Specified by:
    
    copy in class ArcLabelledImmutableGraph
    
    Returns:
    
    a flyweight copy of this immutable graph.
    
    See Also:
    
    FlyweightPrototype
  - nodeIterator
```
public ArcLabelledNodeIterator nodeIterator(long from)
```
    Description copied from class: ArcLabelledImmutableGraph
    
    Returns a node iterator for scanning the graph sequentially, starting from the given node.
    
    Overrides:
    
    nodeIterator in class ArcLabelledImmutableGraph
    
    Parameters:
    
    from - the node from which the iterator will iterate.
    
    Returns:
    
    an ArcLabelledNodeIterator for accessing nodes, successors and their labels sequentially.
    
    See Also:
    
    ImmutableGraph.nodeIterator()
  - numNodes
```
public long numNodes()
```
    Description copied from class: ImmutableGraph
    
    Returns the number of nodes of this graph.
    Albeit this method is not optional, it is allowed that this method throws an UnsupportedOperationException if this graph has never been entirely traversed using a node iterator. This apparently bizarre behaviour is necessary to support implementations as ArcListASCIIGraph, which do not know the actual number of nodes until a traversal has been completed.
    
    Specified by:
    
    numNodes in class ImmutableGraph
    
    Returns:
    
    the number of nodes.
  - randomAccess
```
public boolean randomAccess()
```
    Description copied from class: ImmutableGraph
    
    Checks whether this graph provides random access to successor lists.
    
    Specified by:
    
    randomAccess in class ImmutableGraph
    
    Returns:
    
    true if this graph provides random access to successor lists.
  - hasCopiableIterators
```
public boolean hasCopiableIterators()
```
    Description copied from class: ImmutableGraph
    
    Whether the node iterators returned by this graph support NodeIterator.copy(long).
    
    Overrides:
    
    hasCopiableIterators in class ImmutableGraph
    
    Returns:
    
    true if this graph provides copiable iterators.
  - successorBigArray
```
public long[][] successorBigArray(long x)
```
    Description copied from class: ImmutableGraph
    
    Returns a reference to a big array containing the successors of a given node.
    The returned big array may contain more entries than the outdegree of x. However, only those with indices from 0 (inclusive) to the outdegree of x (exclusive) contain valid data.
    
    Overrides:
    
    successorBigArray in class ImmutableGraph
    
    Parameters:
    
    x - a node.
    
    Returns:
    
    a big array whose first elements are the successors of the node; the array must not be modified by the caller.
  - outdegree
```
public long outdegree(long x)
```
    Description copied from class: ImmutableGraph
    
    Returns the outdegree of a node.
    
    Specified by:
    
    outdegree in class ImmutableGraph
    
    Parameters:
    
    x - a node.
    
    Returns:
    
    the outdegree of the given node.
  - labelBigArray
```
public Label[][] labelBigArray(long x)
```
    Description copied from class: ArcLabelledImmutableGraph
    
    Returns a reference to an array containing the labels of the arcs going out of a given node in the same order as the order in which the corresponding successors are returned by ArcLabelledImmutableGraph.successors(long).
    The returned array may contain more entries than the outdegree of x. However, only those with indices from 0 (inclusive) to the outdegree of x (exclusive) contain valid data.
    
    Overrides:
    
    labelBigArray in class ArcLabelledImmutableGraph
    
    Returns:
    
    an array whose first elements are the labels of the arcs going out of x; the array must not be modified by the caller.
  - successors
```
public ArcLabelledNodeIterator.LabelledArcIterator successors(long x)
```
    Description copied from class: ImmutableGraph
    
    Returns a lazy iterator over the successors of a given node. The iteration terminates when -1 is returned.
    
    Specified by:
    
    successors in class ArcLabelledImmutableGraph
    
    Parameters:
    
    x - a node.
    
    Returns:
    
    a lazy iterator over the successors of the node.
  - prototype
```
public Label prototype()
```
    Description copied from class: ArcLabelledImmutableGraph
    
    Returns a prototype of the labels used by this graph. The prototype can be used to produce new copies, but must not be modified by the caller.
    
    Specified by:
    
    prototype in class ArcLabelledImmutableGraph
    
    Returns:
    
    a prototype for the labels of this graph.

Class UnionArcLabelledImmutableGraph

Remarks about the implementation

Nested Class Summary

Nested classes/interfaces inherited from class it.unimi.dsi.big.webgraph.ImmutableGraph

Field Summary

Fields inherited from class it.unimi.dsi.big.webgraph.labelling.ArcLabelledImmutableGraph

Fields inherited from class it.unimi.dsi.big.webgraph.ImmutableGraph

Constructor Summary

Method Summary

Methods inherited from class it.unimi.dsi.big.webgraph.labelling.ArcLabelledImmutableGraph

Methods inherited from class it.unimi.dsi.big.webgraph.ImmutableGraph

Methods inherited from class java.lang.Object

Constructor Detail

UnionArcLabelledImmutableGraph

Method Detail

copy

nodeIterator

numNodes

randomAccess

hasCopiableIterators

successorBigArray

outdegree

labelBigArray

successors

prototype