There are two classes for polygonal lines in JavaView. PgPolygon contains a single polygonal line implicitly determined by a sequence of vertices. PgPolygonSet contains a number of polygonal lines and a set of vertices. Each line is determines by the list of indices of their vertices. This applet shows a sample instance of PgPolygonSet.
View source code: PaPolygonSet.java of applet, PjPolygonSet.java of project.