code: public boolean replace(Object oldObj, Object newObj)
      {  
          if (nest != null)
          {
              return nest.replace(oldObj, newObj);
          }
          else
          {
              int sz = elements.size();
              for (int i = 0; i < sz; i++)
              {
                  if (elements.get(i) == oldObj)
                  {
                      elements.set(i,newObj);
                      return true;
                  }     
              }
          }
          
          return false;
      }
docs: Replace an object within the composite.