structure
Class Edge

java.lang.Object
  |
  +--structure.Edge

Direct Known Subclasses:

ComparableEdge

public class Edge

extends Object

A class implementing common edge type among graphs. This class supports both directed and undirected edges. Edge may also have visited flags set and cleared.

Typical usage:

     Graph g = new GraphListDirected();
     g.add("harry");
     g.add("sally");
     g.addEdge("harry","sally","friendly");
     Edge e = g.getEdge("harry","sally");
     Object label = e.label();
     if(e.isDirected()){
          Vertex source = e.here();
          Vertex destination = e.there();
     }
     e.visit();
     e.reset();
     ...
 

See Also:

Graph

Field Summary

protected boolean	directed Whether or not this edge is directed.
protected Object	label Label associated with edge.
protected boolean	visited Whether or not this edge has been visited.
protected Object[]	vLabel Two element array of vertex labels.

Constructor Summary

Edge(Object vtx1, Object vtx2, Object label, boolean directed)
Construct a (possibly directed) edge between two labeled vertices.

Method Summary

boolean	equals(Object o) Test for equality of edges.
int	hashCode() Returns hashcode associated with edge.
Object	here() Returns the first vertex (or source if directed).
boolean	isDirected() Check to see if edge is directed.
boolean	isVisited() Check to see if edge has been visited.
Object	label() Get label associated with edge.
void	reset() Clear the visited flag associated with edge.
void	setLabel(Object label) Sets the label associated with the edge.
Object	there() Returns the second vertex (or source if undirected).
String	toString() Construct a string representation of edge.
boolean	visit() Test and set visited flag on vertex.

Methods inherited from class java.lang.Object

, clone, finalize, getClass, notify, notifyAll, registerNatives, wait, wait, wait

Field Detail

vLabel

protected Object[] vLabel

Two element array of vertex labels. When necessary, first element is source.

label

protected Object label

Label associated with edge. May be null.

visited

protected boolean visited

Whether or not this edge has been visited.

directed

protected boolean directed

Whether or not this edge is directed.

Constructor Detail

Edge

public Edge(Object vtx1,
            Object vtx2,
            Object label,
            boolean directed)

Construct a (possibly directed) edge between two labeled vertices. When edge is directed, vtx1 specifies source. When undirected, order of vertices is unimportant. Label on edge is any type, and may be null. Edge is initially unvisited.

Parameters:

vtx1 - The label of a vertex (source if directed).

vtx2 - The label of another vertex (destination if directed).

label - The label associated with the edge.

directed - True iff this edge is directed.

Method Detail

here

public Object here()

Returns the first vertex (or source if directed).

Postcondition:

returns first node in edge

Returns:

A vertex; if directed, the source.

there

public Object there()

Returns the second vertex (or source if undirected).

Postcondition:

returns second node in edge

Returns:

A vertex; if directed, the destination.

setLabel

public void setLabel(Object label)

Sets the label associated with the edge. May be null.

Parameters:

label - Any object to label edge, or null.

Postcondition:

sets label of this edge to label

label

public Object label()

Get label associated with edge.

Postcondition:

returns label associated with this edge

Returns:

The label found on the edge.

visit

public boolean visit()

Test and set visited flag on vertex.

Postcondition:

visits edge, returns whether previously visited

Returns:

True iff edge was visited previously.

isVisited

public boolean isVisited()

Check to see if edge has been visited.

Postcondition:

returns true iff edge has been visited

Returns:

True iff the edge has been visited.

isDirected

public boolean isDirected()

Check to see if edge is directed.

Postcondition:

returns true iff edge is directed

Returns:

True iff the edge has been visited.

reset

public void reset()

Clear the visited flag associated with edge.

Postcondition:

resets edge's visited flag to initial state

hashCode

public int hashCode()

Returns hashcode associated with edge.

Overrides:

hashCode in class Object

Postcondition:

returns suitable hashcode

Returns:

An integer code suitable for hashing.

equals

public boolean equals(Object o)

Test for equality of edges. Undirected edges are equal if they connect the same vertices. Directed edges must have same direction.

Overrides:

equals in class Object

Parameters:

o - The other edge.

Postcondition:

returns true iff edges connect same vertices

Returns:

True iff this edge is equal to other edge.

toString

public String toString()

Construct a string representation of edge.

Overrides:

toString in class Object

Postcondition:

returns string representation of edge

Returns:

String representing edge.