code: public void renumberIDs()
     {
        if (!isEmpty())
        {
           Collections.sort(this);
           T firstEntity = get(0);
           int id = NumberHelper.getInt(firstEntity.getID());
           if (id != 0)
           {
              id = 1;
           }
  
           for (T entity : this)
           {
              entity.setID(Integer.valueOf(id++));
           }
        }
     }
docs: This method can be called to ensure that the IDs of all
  entities are sequential, and start from an
  appropriate point. If entities are added to and removed from
  this list, then the project is loaded into Microsoft
  project, if the ID values have gaps in the sequence, there will
  be blank rows shown.