/** Dispatch the edgeTailChanged() event to the listeners. */
 public void edgeTailChanged(GraphEvent e) {
   for (Iterator i = listeners(); i.hasNext(); ) {
     GraphListener l = (GraphListener) i.next();
     l.edgeTailChanged(e);
   }
 }
 /** Dispatch the nodeRemoved() event to each of the listeners. */
 public void nodeRemoved(GraphEvent e) {
   for (Iterator i = listeners(); i.hasNext(); ) {
     GraphListener l = (GraphListener) i.next();
     l.nodeRemoved(e);
   }
 }
 /** Dispatch the structureChanged() event to each of the listeners. */
 public void structureChanged(GraphEvent e) {
   for (Iterator i = listeners(); i.hasNext(); ) {
     GraphListener l = (GraphListener) i.next();
     l.structureChanged(e);
   }
 }