Package it.unimi.dsi.webgraph

Class NodeIterator

java.lang.Object
it.unimi.dsi.webgraph.NodeIterator
All Implemented Interfaces:
IntIterator, Iterator<Integer>, PrimitiveIterator<Integer,​IntConsumer>, PrimitiveIterator.OfInt
Direct Known Subclasses:
ArcLabelledNodeIterator
public abstract class NodeIterator
extends Object
implements IntIterator
This interface extends IntIterator and is used to scan a graph, that is, to read its nodes and their successor lists sequentially. The IntIterator.nextInt() method returns the node that will be scanned. After a call to this method, calling successors() or successorArray() will return the list of successors.

Implementing subclasses can override either successors() or successorArray(), but at least one of them must be implemented.

The copy(int) methods is in fact optional, but should be implemented whenever the graph can be scanned more than once.

  • Field Details

    • EMPTY

      public static final NodeIterator EMPTY
      An empty node iterator.

  • Constructor Details

    • NodeIterator

      public NodeIterator()

  • Method Details

    • outdegree

      public abstract int outdegree()
      Returns the outdegree of the current node.
      Returns:
      the outdegree of the current node.

    • successors

      public LazyIntIterator successors()
      Returns a lazy iterator over the successors of the current node. The iteration terminates when -1 is returned.

      This implementation just wraps the array returned by successorArray().

      Returns:
      a lazy iterator over the successors of the current node.

    • successorArray

      public int[] successorArray()
      Returns a reference to an array containing the successors of the current node.

      The returned array may contain more entries than the outdegree of the current node. However, only those with indices from 0 (inclusive) to the outdegree of the current node (exclusive) contain valid data.

      Returns:
      an array whose first elements are the successors of the current node; the array must not be modified by the caller.
      Implementation Specification:
      This implementation just unwrap the iterator returned by successors().

    • copy

      public NodeIterator copy​(int upperBound)
      Creates a copy of this iterator that will never return nodes ≥ the specified bound; the copy must be accessible by a different thread. Optional operation (it should be implemented by all classes that allow to scan the graph more than once).
      Parameters:
      upperBound - the upper bound.
      Returns:
      a copy of this iterator, with the given upper bound.
      Implementation Specification:
      This implementation just throws an UnsupportedOperationException. It should be kept in sync with the result of ImmutableGraph.hasCopiableIterators().