updated version 1

drawing/Graph.pde

@@ -9,4 +9,10 @@ class Graph{
     }
     return true;
   }
+
+  boolean check3edges_per_vertex(Vertex v){ 
+      if(v.E.size()<3) return true;
+      if(v.E.size()>=3) return false; 
+    return true;
+  }
 }

drawing/drawing.pde

@@ -117,41 +117,28 @@ void mouse_over_BUTTON(){
    text("Reset",rectX2+rectwidth/8,rectY2+rectheight/2);
 }
 
-
-
 void mouseClicked(){
  if(check_mouse_over_button(rectX1,rectY1,rectheight,rectwidth)){
   //draw edges should be implemented by pressing button.
     if (G.V.size()<=3) throw new RuntimeException("Requires at least 5 points"); 
-     ArrayList index=new ArrayList ();
     for(int i=0;i<G.V.size();i++){
-      for(int r=0;r<G.V.size();r++){
-        index.add(r);
-       }
-      index.remove(i);
-     for(int j=0;j<=3;j++){
+     do{
          stroke(0,0,255);
          strokeWeight(2);
-         int k=int(random(index.size()));  
-         int l=(Integer)index.get(k);  
+         int l= int(random(G.V.size()));
          println(l);
-           //add the drawn edge to the graph and the Vertex arraylist
-         //if(G.ValidNewEdge(G.V.get(i),G.V.get(l))){
+        //add the drawn edge to the graph 
+         if(G.ValidNewEdge(G.V.get(i),G.V.get(l))){   //have to check the whether the randomly selected vertex has three edges????
            G.E.add(new Edge(G.V.get(i),G.V.get(l)));     
            line(G.V.get(i).x,G.V.get(i).y,G.V.get(l).x,G.V.get(l).y);
-           index.remove(k);
-        }
-      }
-        //remove the repeatedly added edges from the edge list
-     for(int i=0;i<G.E.size();++i){
-         for(int j=0;j<G.E.size();++j)
-           if(G.E.get(i).v2==G.E.get(j).v1 && G.E.get(i).v1==G.E.get(j).v2)
-             G.E.remove(j);
          }
+        }while(G.check3edges_per_vertex(G.V.get(i)));
+      }
      }
-       if(check_mouse_over_button(rectX2,rectY2,rectheight,rectwidth))
-
+       if(check_mouse_over_button(rectX2,rectY2,rectheight,rectwidth)){
           G.E.clear();
+          G.V.clear();
+        }
 }