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Interface structure.Graph

public interface Graph

extends Collection

See Also:

GraphList, GraphMatrix

add(Object)

Add a vertex to the graph.

addEdge(Object, Object, Object)

Add an edge between two vertices within the graph.

clear()

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

contains(Object)

Test for vertex membership.

containsEdge(Object, Object)

Test for edge membership.

degree(Object)

Determine out degree of vertex.

edgeCount()

Determine the number of edges in graph.

edges()

Construct an iterator over all edges.

elements()

Construct vertex iterator.

get(Object)

Get reference to actual label of vertex.

getEdge(Object, Object)

Get reference to actual edge.

isDirected()

Determine if graph is directed.

isEmpty()

Determine if graph is empty.

isVisited(Object)

Return visited flag of vertex.

isVisitedEdge(Edge)

Return visited flag of edge.

neighbors(Object)

Construct an adjacent vertex iterator.

remove(Object)

Remove a vertex from the graph.

removeEdge(Object, Object)

Remove possible edge between vertices labeled vLabel1 and vLabel2.

reset()

Clear visited flags of edges and vertices.

size()

Determine number of vertices within graph.

visit(Object)

Test and set visited flag of vertex.

visitEdge(Edge)

Test and set visited flag of edge.

public abstract void add(Object label)

Add a vertex to the graph.

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.

Parameters:

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

public abstract void addEdge(Object vtx1,
                             Object vtx2,
                             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.

Precondition:

vtx1 and vtx2 are labels of existing vertices

Postcondition:

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

Parameters:

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

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

label - Label associated with the edge.

public abstract Object remove(Object label)

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

Precondition:

label is non-null vertex label

Postcondition:

vertex with "equals" label is removed, if found

Parameters:

label - The label of the vertex within the graph.

Returns:

The label associated with the vertex.

public abstract Object removeEdge(Object vLabel1,
                                  Object vLabel2)

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

Precondition:

vLabel1 and vLabel2 are labels of existing vertices

Postcondition:

edge is removed, its label is returned

Parameters:

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

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

Returns:

The label associated with the edge removed.

public abstract Object get(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.

Postcondition:

returns actual label of indicated vertex

Parameters:

label - The label of the vertex sought.

Returns:

The actual label, or null if none is found.

public abstract Edge getEdge(Object label1,
                             Object label2)

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

Postcondition:

returns actual edge between vertices.

Parameters:

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

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

Returns:

The edge, if found, or null.

public abstract boolean contains(Object label)

Test for vertex membership.

Postcondition:

returns true iff vertex with "equals" label exists.

Parameters:

label - The label of the vertex sought.

Returns:

True iff vertex with matching label is found.

public abstract boolean containsEdge(Object vLabel1,
                                     Object vLabel2)

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

Postcondition:

returns true iff edge with "equals" label exists

Parameters:

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

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

Returns:

True iff the edge exists within the graph.

public abstract boolean visit(Object label)

Test and set visited flag of vertex.

Postcondition:

sets visited flag on vertex, returns previous value

Parameters:

label - Label of vertex to be visited.

Returns:

Previous value of visited flag on vertex.

public abstract boolean visitEdge(Edge e)

Test and set visited flag of edge.

Precondition:

sets visited flag on edge; returns previous value

Parameters:

e - Edge object that is part of graph.

Returns:

Previous value of the Edge's visited flag.

public abstract boolean isVisited(Object label)

Return visited flag of vertex.

Postcondition:

returns visited flag on labeled vertex

Parameters:

label - Label of vertex.

Returns:

True if vertex has been visited.

public abstract boolean isVisitedEdge(Edge e)

Return visited flag of edge.

Postcondition:

returns visited flag on edge between vertices

Parameters:

e - Edge of graph to be considered.

Returns:

True if the edge has been visited.

public abstract void reset()

Clear visited flags of edges and vertices.

Postcondition:

resets visited flags to false

public abstract int size()

Determine number of vertices within graph.

Postcondition:

returns the number of vertices in graph

Returns:

The number of vertices within graph.

public abstract int degree(Object label)

Determine out degree of vertex.

Precondition:

label labels an existing vertex

Postcondition:

returns the number of vertices adjacent to vertex

Parameters:

label - Label associated with vertex.

Returns:

The number of edges with this vertex as source.

public abstract int edgeCount()

Determine the number of edges in graph.

Postcondition:

returns the number of edges in graph

Returns:

Number of edges in graph.

public abstract Iterator elements()

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

Postcondition:

returns iterator across all vertices of graph

Returns:

Iterator traversing vertices in graph.

public abstract Iterator neighbors(Object label)

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

Precondition:

label is label of vertex in graph

Postcondition:

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

Parameters:

label - Label of the vertex.

Returns:

Iterator traversing the adjacent vertices of labeled vertex.

public abstract Iterator edges()

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

Postcondition:

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

Returns:

Iterator over edges.

public abstract void clear()

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

Postcondition:

removes all vertices from graph

public abstract boolean isEmpty()

Determine if graph is empty.

Postcondition:

returns true if graph contains no vertices

Returns:

True iff there are no vertices in graph.

public abstract boolean isDirected()

Determine if graph is directed.

Postcondition:

returns true if edges of graph are directed

Returns:

True iff the graph is directed.

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