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## org.jgrapht.traverse
Class BreadthFirstIterator<V,E>

    java.lang.Object
      org.jgrapht.traverse.AbstractGraphIterator<V,E>
          org.jgrapht.traverse.CrossComponentIterator<V,E,java.lang.Object>
              org.jgrapht.traverse.BreadthFirstIterator<V,E>

All Implemented Interfaces:
  java.util.Iterator<V>, GraphIterator<V,E>

    public class BreadthFirstIterator<V,E>

extends CrossComponentIterator<V,E,java.lang.Object>

A breadth-first iterator for a directed and an undirected graph. For this iterator to work correctly the graph must not be modified during iteration. Currently there are no means to ensure that, nor to fail-fast. The results of such modifications are undefined.

Since:
  Jul 19, 2003
Author:
  Barak Naveh

Nested Class Summary

Nested classes/interfaces inherited from class org.jgrapht.traverse.CrossComponentIterator
`CrossComponentIterator.VisitColor`

Field Summary

Fields inherited from class org.jgrapht.traverse.AbstractGraphIterator
`nListeners`

Constructor Summary
`BreadthFirstIterator(Graph<V,E> g)` Creates a new breadth-first iterator for the specified graph.
`BreadthFirstIterator(Graph<V,E> g, V startVertex)` Creates a new breadth-first iterator for the specified graph.

Method Summary
`protected void` | `encounterVertex(V vertex, E edge)` Update data structures the first time we see a vertex.
`protected void` | `encounterVertexAgain(V vertex, E edge)` Called whenever we re-encounter a vertex.
`protected boolean` | `isConnectedComponentExhausted()` Returns `true` if there are no more uniterated vertices in the currently iterated connected component; `false` otherwise.
`protected V` | `provideNextVertex()` Returns the vertex to be returned in the following call to the iterator `next` method.

Methods inherited from class org.jgrapht.traverse.CrossComponentIterator
`finishVertex, getGraph, getSeenData, hasNext, isSeenVertex, next, putSeenData`

Methods inherited from class org.jgrapht.traverse.AbstractGraphIterator
`addTraversalListener, fireConnectedComponentFinished, fireConnectedComponentStarted, fireEdgeTraversed, fireVertexFinished, fireVertexTraversed, isCrossComponentTraversal, isReuseEvents, remove, removeTraversalListener, setCrossComponentTraversal, setReuseEvents`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### BreadthFirstIterator

    public BreadthFirstIterator(Graph<V,E> g)

  Creates a new breadth-first iterator for the specified graph.

  Parameters:
    `g` - the graph to be iterated.

### BreadthFirstIterator

    public BreadthFirstIterator(Graph<V,E> g,
                                V startVertex)

  Creates a new breadth-first iterator for the specified graph. Iteration will start at the specified start vertex and will be limited to the connected component that includes that vertex. If the specified start vertex is `null`, iteration will start at an arbitrary vertex and will not be limited, that is, will be able to traverse all the graph.

  Parameters:
    `g` - the graph to be iterated.
    `startVertex` - the vertex iteration to be started.

Method Detail

### isConnectedComponentExhausted

    protected boolean isConnectedComponentExhausted()

  Description copied from class: `CrossComponentIterator`
  Returns `true` if there are no more uniterated vertices in the currently iterated connected component; `false` otherwise.

  Specified by:
    `isConnectedComponentExhausted` in class `CrossComponentIterator<V,E,java.lang.Object>`
  Returns:
    `true` if there are no more uniterated vertices in the currently iterated connected component; `false` otherwise.
  See Also:
    `CrossComponentIterator.isConnectedComponentExhausted()`

### encounterVertex

    protected void encounterVertex(V vertex,
                                   E edge)

  Description copied from class: `CrossComponentIterator`
  Update data structures the first time we see a vertex.

  Specified by:
    `encounterVertex` in class `CrossComponentIterator<V,E,java.lang.Object>`
  Parameters:
    `vertex` - the vertex encountered
    `edge` - the edge via which the vertex was encountered, or null if the vertex is a starting point
  See Also:
    `CrossComponentIterator.encounterVertex(Object, Object)`

### encounterVertexAgain

    protected void encounterVertexAgain(V vertex,
                                        E edge)

  Description copied from class: `CrossComponentIterator`
  Called whenever we re-encounter a vertex. The default implementation does nothing.

  Specified by:
    `encounterVertexAgain` in class `CrossComponentIterator<V,E,java.lang.Object>`
  Parameters:
    `vertex` - the vertex re-encountered
    `edge` - the edge via which the vertex was re-encountered
  See Also:
    `CrossComponentIterator.encounterVertexAgain(Object, Object)`

### provideNextVertex

    protected V provideNextVertex()

  Description copied from class: `CrossComponentIterator`
  Returns the vertex to be returned in the following call to the iterator `next` method.

  Specified by:
    `provideNextVertex` in class `CrossComponentIterator<V,E,java.lang.Object>`
  Returns:
    the next vertex to be returned by this iterator.
  See Also:
    `CrossComponentIterator.provideNextVertex()`

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