code: public void setSearchSubtree(boolean searchSubtree) {
          int searchScope = searchSubtree ? SearchControls.SUBTREE_SCOPE : SearchControls.ONELEVEL_SCOPE;
          searchControls.setSearchScope(searchScope);
      }
docs: If set to true, a subtree scope search will be performed. If false a single-level search is used.
  
  @param searchSubtree set to true to enable searching of the entire tree below the <tt>groupSearchBase</tt>.