Update numbers -shows expecting in typecasting.. pl help

Question

Hi
I have a Object class Field Group with methods like setgroup id,get groupid,get label, set label .
I need to update the group id when the List <fieldgroup> is updated. for updating i worte a code saying
g_list is a List<FieldGroup>
public void updateidNumbers()
     for (int i = 0 ; i < g_list.size(); i ++)
               int c = g_list.size();
               System.out.print(c);
               FieldGroup a = g_list.get(i);
               a.setGroupId(new BigDecimal(i));
               System.out.print(a.getlabel());
where setGroupId return a bigdecimal value ...
My probelm is that it showing a Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: java.lang.String
     at this line      FieldGroup a = g_list.get(i);
please help
thanks in Advance

Answer 1

public class ViewTreeModel implements TreeModel
     private Vector<TreeModelListener> f_treeModelListeners; // TreeModelListeners associated with the tree
//     private View f_view;//A View For ProjectField
//     private View g_view;// A View For ProjectFieldGroup
     List <ProjectFieldGroup>g_list;//Top Level List for Project Field Group
     List <ProjectField>f_list ;//Top Level List for Project Field Group
     private View root; // root will be a node
      * @param view
      * @param grouplist
      * @param fieldlist
     public ViewTreeModel(List<ProjectFieldr> field , List<ProjectFieldGroup>group )
          f_list = field;
          g_list = group;
          f_treeModelListeners = new Vector<TreeModelListener>();
/**Add a  Group
* @param pathtoParent 
* @param groupId
* @param content
     public void addgroup(TreePath path ,int groupid, Object content)
          Object parent =path.getLastPathComponent();
     //     ((List)parent).add(groupid, content);
          if (parent instanceof List)
               ((List)parent).add(groupid ,content);}
          updateidNumbers();
          fireStructureChange();
     public void add(TreePath path , int index , Object obj)
      * Update all the  group id and parent id of ProjectFieldGroupDescriptor in the view
     public void updateSequenceNumbers()
          for(int i = 0 ; i < f_list.size();i++)
               f_list.get(i).setSequence(new BigDecimal(i));
     public void updateidNumbers()
          int i = 0 ;
          int g = g_list.size();
     //     System.out.print(g);
          Object a = (g_list.get(i));
          System.out.print(a);
          (g_list.get(i)).setGroupId(new BigDecimal(i));
          int c = g_list.size();
          for (int i = 0 ; i < g_list.size(); i ++)
          //     System.out.print(c);
                Object a =      g_list.get(i);
     /*          ProjectFieldGroupDescriptor  a = (ProjectFieldGroupDescriptor)g_list.get(i);
               a.setGroupId(new BigDecimal(i));
               //     b = (g_list.get(i)).setGroupId(new BigDecimal(i)); //Orginal Statement
               System.out.print(a.getLabel());*/
               System.out.print(a);
     }