Java adjacency list implementation with a HashMap -


i trying create adjacency list class. trying hashmap. each bucket points list of lists last list being of size 3. unfortunately haven't managed working. appreciated. error line of code

ulist.get(0).add(v); ulist.get(1).add(capacity); ulist.get(2).add(flow);

/* adjacency list */ public class adjacencylist {     map< integer, arraylist<arraylist<integer>> > adjlist;      //constructor     public adjacencylist(int v)     {         // 0 -> [ [v1,capacity1,flow1] , [v2,capacity2,flow2] , ...]         adjlist = new hashmap< integer, arraylist<arraylist<integer> >>();         for(int = 1; i<v+1; i++)         {             adjlist.put(i, new arraylist<arraylist<integer>>());         }      }      // method adding edge (->node)      // - current capacity (aka remaining flow)     // - current flow     public void addedge(int u, int v, int capacity, int flow)     {         arraylist<arraylist<integer>> ulist = new arraylist<arraylist<integer>>();         system.out.println("ul: " + ulist);         ulist.get(0).add(v); ulist.get(1).add(capacity); ulist.get(2).add(flow);         adjlist.put(u, ulist);      }      // method retrieving list of children u (u->v1,v2,v3,...)     public arraylist<arraylist<integer>> getedge(int u)     {         return adjlist.get(u);     }  }


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