structure
Class GraphList

java.lang.Object
  structure.AbstractStructure
      structure.GraphList

All Implemented Interfaces:

Graph, Structure

Direct Known Subclasses:

GraphListDirected, GraphListUndirected

public abstract class GraphList
extends AbstractStructure
implements Graph

Implementation of graph using adjacency lists. Edges are stored in lists off of vertex structure. Class is abstract: you must use GraphListDirected or GraphListUndirected to construct particular instances of graphs. Typical usage:

     Graph g = new GraphListDirected();
     g.add("harry");
     g.add("sally");
     g.addEdge("harry","sally","friendly");
     ...
 

See Also:

GraphListDirected, GraphListUndirected, GraphMatrix

Field Summary

protected Map	dict Map associating vertex labels with vertex structures.
protected boolean	directed Whether or not graph is directed.

Constructor Summary

protected

GraphList(boolean dir) Constructor of directed/undirected GraphList.

Method Summary

void	add(java.lang.Object label) Add a vertex to the graph.
abstract void	addEdge(java.lang.Object v1, java.lang.Object v2, java.lang.Object label) Add an edge between two vertices within the graph.
void	clear() Remove all vertices (and thus, edges) of the graph.
boolean	contains(java.lang.Object label) Test for vertex membership.
boolean	containsEdge(java.lang.Object vLabel1, java.lang.Object vLabel2) Test for edge membership.
int	degree(java.lang.Object label) Determine out degree of vertex.
abstract int	edgeCount() Determine the number of edges in graph.
java.util.Iterator	edges() Construct an iterator over all edges.
java.lang.Object	get(java.lang.Object label) Get reference to actual label of vertex.
Edge	getEdge(java.lang.Object label1, java.lang.Object label2) Get reference to actual edge.
boolean	isDirected() Determine if graph is directed.
boolean	isEmpty() Determine if graph is empty.
boolean	isVisited(java.lang.Object label) Return visited flag of vertex.
boolean	isVisitedEdge(Edge e) Return visited flag of edge.
java.util.Iterator	iterator() Construct vertex iterator.
java.util.Iterator	neighbors(java.lang.Object label) Construct an adjacent vertex iterator.
abstract java.lang.Object	remove(java.lang.Object label) Remove a vertex from the graph.
abstract java.lang.Object	removeEdge(java.lang.Object vLabel1, java.lang.Object vLabel2) Remove possible edge between vertices labeled vLabel1 and vLabel2.
void	reset() Clear visited flags of edges and vertices.
int	size() Determine number of vertices within graph.
boolean	visit(java.lang.Object label) Test and set visited flag of vertex.
boolean	visitEdge(Edge e) Test and set visited flag of edge.

Methods inherited from class structure.AbstractStructure

elements, hashCode, values

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface structure.Structure

elements, values

Field Detail

dict

protected Map dict

Map associating vertex labels with vertex structures.

directed

protected boolean directed

Whether or not graph is directed.

Constructor Detail

GraphList

protected GraphList(boolean dir)

Constructor of directed/undirected GraphList. Protected constructor.

Parameters:

dir - True if graph is to be directed.

Method Detail

add

public void add(java.lang.Object label)

Add a vertex to the graph.

Specified by:

add in interface Graph

Specified by:

add in interface Structure

Parameters:

label - Label of the vertex; should be non-null.

Precondition:

label is a non-null label for vertex

Postcondition:

a vertex with label is added to graph; if vertex with label is already in graph, no action

addEdge

public abstract void addEdge(java.lang.Object v1,
                             java.lang.Object v2,
                             java.lang.Object label)

Add an edge between two vertices within the graph. Edge is directed iff graph is directed. Duplicate edges are silently replaced. Labels on edges may be null.

Specified by:

addEdge in interface Graph

Parameters:

vtx1 - First (or source, if directed) vertex.

vtx2 - Second (or destination, if directed) vertex.

label - Label associated with the edge.

Precondition:

vtx1 and vtx2 are labels of existing vertices

Postcondition:

an edge (possibly directed) is inserted between vtx1 and vtx2.

remove

public abstract java.lang.Object remove(java.lang.Object label)

Remove a vertex from the graph. Associated edges are also removed. Non-vertices are silently ignored.

Specified by:

remove in interface Graph

Specified by:

remove in interface Structure

Parameters:

label - The label of the vertex within the graph.

Returns:

The label associated with the vertex.

Precondition:

label is non-null vertex label

Postcondition:

vertex with "equals" label is removed, if found

removeEdge

public abstract java.lang.Object removeEdge(java.lang.Object vLabel1,
                                            java.lang.Object vLabel2)

Remove possible edge between vertices labeled vLabel1 and vLabel2. Directed edges consider vLabel1 to be the source.

Specified by:

removeEdge in interface Graph

Parameters:

vLabel1 - First (or source, if directed) vertex.

vLabel2 - Second (or destination, if directed) vertex.

Returns:

The label associated with the edge removed.

Precondition:

vLabel1 and vLabel2 are labels of existing vertices

Postcondition:

edge is removed, its label is returned

get

public java.lang.Object get(java.lang.Object label)

Get reference to actual label of vertex. Vertex labels are matched using their equals method, which may or may not test for actual equivalence. Result remains part of graph.

Specified by:

get in interface Graph

Parameters:

label - The label of the vertex sought.

Returns:

The actual label, or null if none is found.

Postcondition:

returns actual label of indicated vertex

getEdge

public Edge getEdge(java.lang.Object label1,
                    java.lang.Object label2)

Get reference to actual edge. Edge is identified by the labels on associated vertices. If edge is directed, the label1 indicates source.

Specified by:

getEdge in interface Graph

Parameters:

label1 - The first (or source, if directed) vertex.

label2 - The second (or destination, if directed) vertex.

Returns:

The edge, if found, or null.

Postcondition:

returns actual edge between vertices

contains

public boolean contains(java.lang.Object label)

Test for vertex membership.

Specified by:

contains in interface Graph

Specified by:

contains in interface Structure

Overrides:

contains in class AbstractStructure

Parameters:

label - The label of the vertex sought.

Returns:

True iff vertex with matching label is found.

Postcondition:

returns true iff vertex with "equals" label exists

containsEdge

public boolean containsEdge(java.lang.Object vLabel1,
                            java.lang.Object vLabel2)

Test for edge membership. If edges are directed, vLabel1 indicates source.

Specified by:

containsEdge in interface Graph

Parameters:

vLabel1 - First (or source, if directed) vertex.

vLabel2 - Second (or destination, if directed) vertex.

Returns:

True iff the edge exists within the graph.

Postcondition:

returns true iff edge with "equals" label exists

visit

public boolean visit(java.lang.Object label)

Test and set visited flag of vertex.

Specified by:

visit in interface Graph

Parameters:

label - Label of vertex to be visited.

Returns:

Previous value of visited flag on vertex.

Postcondition:

sets visited flag on vertex, returns previous value

visitEdge

public boolean visitEdge(Edge e)

Test and set visited flag of edge.

Specified by:

visitEdge in interface Graph

Parameters:

e - Edge object that is part of graph.

Returns:

Previous value of the Edge's visited flag.

Precondition:

sets visited flag on edge; returns previous value

isVisited

public boolean isVisited(java.lang.Object label)

Return visited flag of vertex.

Specified by:

isVisited in interface Graph

Parameters:

label - Label of vertex.

Returns:

True if vertex has been visited.

Postcondition:

returns visited flag on labeled vertex

isVisitedEdge

public boolean isVisitedEdge(Edge e)

Return visited flag of edge.

Specified by:

isVisitedEdge in interface Graph

Parameters:

e - Edge of graph to be considered.

Returns:

True if the edge has been visited.

Postcondition:

returns visited flag on edge between vertices

reset

public void reset()

Clear visited flags of edges and vertices.

Specified by:

reset in interface Graph

Postcondition:

resets visited flags to false

size

public int size()

Determine number of vertices within graph.

Specified by:

size in interface Graph

Specified by:

size in interface Structure

Returns:

The number of vertices within graph.

Postcondition:

returns the number of vertices in graph

degree

public int degree(java.lang.Object label)

Determine out degree of vertex.

Specified by:

degree in interface Graph

Parameters:

label - Label associated with vertex.

Returns:

The number of edges with this vertex as source.

Precondition:

label labels an existing vertex

Postcondition:

returns the number of vertices adjacent to vertex

edgeCount

public abstract int edgeCount()

Determine the number of edges in graph.

Specified by:

edgeCount in interface Graph

Returns:

Number of edges in graph.

Postcondition:

returns the number of edges in graph

iterator

public java.util.Iterator iterator()

Construct vertex iterator. Vertices are not visited in any guaranteed order.

Specified by:

iterator in interface Graph

Specified by:

iterator in interface Structure

Returns:

AbstractIterator traversing vertices in graph.

See Also:

AbstractIterator, Iterator, Enumeration, Structure.elements()

Postcondition:

returns iterator across all vertices of graph

neighbors

public java.util.Iterator neighbors(java.lang.Object label)

Construct an adjacent vertex iterator. Adjacent vertices (those on destination of edge, if directed) are considered, but not in any guaranteed order.

Specified by:

neighbors in interface Graph

Parameters:

label - Label of the vertex.

Returns:

Iterator traversing the adjacent vertices of labeled vertex.

Precondition:

label is label of vertex in graph

Postcondition:

returns iterator over vertices adj. to vertex each edge beginning at label visited exactly once

edges

public java.util.Iterator edges()

Construct an iterator over all edges. Every directed/undirected edge is considered exactly once. Order is not guaranteed.

Specified by:

edges in interface Graph

Returns:

Iterator over edges.

Postcondition:

returns iterator across edges of graph iterator returns edges; each edge visited once

clear

public void clear()

Remove all vertices (and thus, edges) of the graph.

Specified by:

clear in interface Graph

Specified by:

clear in interface Structure

Postcondition:

removes all vertices from graph

isEmpty

public boolean isEmpty()

Determine if graph is empty.

Specified by:

isEmpty in interface Graph

Specified by:

isEmpty in interface Structure

Overrides:

isEmpty in class AbstractStructure

Returns:

True iff there are no vertices in graph.

Postcondition:

returns true if graph contains no vertices

isDirected

public boolean isDirected()

Determine if graph is directed.

Specified by:

isDirected in interface Graph

Returns:

True iff the graph is directed.

Postcondition:

returns true if edges of graph are directed