TopologicalOrderIterator (JGraphT : a free Java graph library)

java.lang.Object
- org._3pq.jgrapht.traverse.AbstractGraphIterator
- - org._3pq.jgrapht.traverse.CrossComponentIterator
  - - org._3pq.jgrapht.traverse.TopologicalOrderIterator

All Implemented Interfaces:

java.util.Iterator, GraphIterator
```
public class TopologicalOrderIterator
extends CrossComponentIterator
```
Implements topological order traversal for a directed graph. A topological sort is a permutation p of the vertices of a graph such that an edge (i,j) implies that i appears before j in p (Skiena 1990, p. 208). See also http://mathworld.wolfram.com/TopologicalSort.html.
See "Algorithms in Java, Third Edition, Part 5: Graph Algorithms" by Robert Sedgewick and "Data Structures and Algorithms with Object-Oriented Design Patterns in Java" by Bruno R. Preiss for implementation alternatives. The latter can be found online at http://www.brpreiss.com/books/opus5/

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:

Dec 18, 2004

Author:

Marden Neubert

Constructor Summary

Constructors
Constructor and Description

TopologicalOrderIterator(DirectedGraph dg)
Creates a new topological order iterator over the directed graph specified.

Constructors
Constructor and Description
`TopologicalOrderIterator(DirectedGraph dg)` Creates a new topological order iterator over the directed graph specified.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected void`	`encounterVertex(java.lang.Object vertex, Edge edge)` Update data structures the first time we see a vertex.
`protected void`	`encounterVertexAgain(java.lang.Object vertex, Edge 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 java.lang.Object`	`provideNextVertex()` Returns the vertex to be returned in the following call to the iterator `next` method.

Methods inherited from class org._3pq.jgrapht.traverse.CrossComponentIterator
getSeenData, hasNext, isSeenVertex, next, putSeenData

Methods inherited from class org._3pq.jgrapht.traverse.AbstractGraphIterator
addTraversalListener, fireConnectedComponentFinished, fireConnectedComponentStarted, fireEdgeTraversed, 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

Methods inherited from interface java.util.Iterator
forEachRemaining

- Constructor Detail
  - TopologicalOrderIterator
```
public TopologicalOrderIterator(DirectedGraph dg)
```
    Creates a new topological order iterator over the directed graph specified. Traversal will start at one of the graphs sources. See the definition of source at http://mathworld.wolfram.com/Source.html.
    
    Parameters:
    
    dg - the directed graph to be iterated.
- 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
    
    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(java.lang.Object vertex,
                               Edge edge)
```
    Description copied from class: CrossComponentIterator
    
    Update data structures the first time we see a vertex.
    
    Specified by:
    
    encounterVertex in class CrossComponentIterator
    
    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, Edge)
  - encounterVertexAgain
```
protected void encounterVertexAgain(java.lang.Object vertex,
                                    Edge edge)
```
    Description copied from class: CrossComponentIterator
    
    Called whenever we re-encounter a vertex. The default implementation does nothing.
    
    Specified by:
    
    encounterVertexAgain in class CrossComponentIterator
    
    Parameters:
    
    vertex - the vertex re-encountered
    
    edge - the edge via which the vertex was re-encountered
    
    See Also:
    
    CrossComponentIterator.encounterVertexAgain(Object, Edge)
  - provideNextVertex
```
protected java.lang.Object 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
    
    Returns:
    
    the next vertex to be returned by this iterator.
    
    See Also:
    
    CrossComponentIterator.provideNextVertex()

Class TopologicalOrderIterator

Constructor Summary

Method Summary

Methods inherited from class org._3pq.jgrapht.traverse.CrossComponentIterator

Methods inherited from class org._3pq.jgrapht.traverse.AbstractGraphIterator

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Iterator

Constructor Detail

TopologicalOrderIterator

Method Detail

isConnectedComponentExhausted

encounterVertex

encounterVertexAgain

provideNextVertex