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

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

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

    public class DepthFirstIterator<V,E>

extends CrossComponentIterator<V,E,CrossComponentIterator.VisitColor>

A depth-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 29, 2003
Author:
  Liviu Rau, Barak Naveh

Nested Class Summary

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

Field Summary
`static java.lang.Object` | `SENTINEL` Sentinel object.

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

Constructor Summary
`DepthFirstIterator(Graph<V,E> g)` Creates a new depth-first iterator for the specified graph.
`DepthFirstIterator(Graph<V,E> g, V startVertex)` Creates a new depth-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.
`java.util.Deque<java.lang.Object>` | `getStack()` Retrieves the LIFO stack of vertices which have been encountered but not yet visited (WHITE).
`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`

Field Detail

### SENTINEL

    public static final java.lang.Object SENTINEL

  Sentinel object. Unfortunately, we can't use null, because ArrayDeque won't accept those. And we don't want to rely on the caller to provide a sentinel object for us. So we have to play typecasting games.

Constructor Detail

### DepthFirstIterator

    public DepthFirstIterator(Graph<V,E> g)

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

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

### DepthFirstIterator

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

  Creates a new depth-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,CrossComponentIterator.VisitColor>`
  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,CrossComponentIterator.VisitColor>`
  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,CrossComponentIterator.VisitColor>`
  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,CrossComponentIterator.VisitColor>`
  Returns:
    the next vertex to be returned by this iterator.
  See Also:
    `CrossComponentIterator.provideNextVertex()`

### getStack

    public java.util.Deque<java.lang.Object> getStack()

  Retrieves the LIFO stack of vertices which have been encountered but not yet visited (WHITE). This stack also contains sentinel entries representing vertices which have been visited but are still GRAY. A sentinel entry is a sequence (v, SENTINEL), whereas a non-sentinel entry is just (v).

  Returns:
    stack

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