Data Structures and Algorithms
with Object-Oriented Design Patterns in Java 
Program 
also declares four methods
each of which returns an Enumeration.
The getIncidentEdges method returns an Enumeration that enumerates
the elements of the 
.
Similarly, the getEmanatingEdges method returns an Enumeration
that enumerates the elements of 
.
The getPredecessors method returns an Enumeration that enumerates
the elements of 
and the getPredecessors method returns an Enumeration
that enumerates 
.
The elements of 
and 
are vertices
whereas the elements of and are edges.
Copyright © 1998 by Bruno R. Preiss, P.Eng. All rights reserved.