How can i make a 2 layer structure?

Hello i try the code below but in the for each i get an error. now
datatype allowed

How can i fix this i need two layers

     public static HashMap<String, HashMap> data = new
LinkedHashMap<String, HashMap>();

     public void getConfig() {
         String strSQL = "";
         JDb db = new JDb();
         db.ConnectDb();
         strSQL = "SELECT " +
                 " CID, " +
                 " ckey," +
                 " cvalue," +
                 " cdescription " +
                 "FROM " +
                 " config " +
                 "ORDER BY " +
                 " ckey";
         db.makeQuery(strSQL);
         try {
             while (db.rs.next()) {
                 HashMap<String, String> c = new LinkedHashMap<String,
String>();
                 c.clear();
                 c.put("CID", db.rs.getString("CID"));
                 c.put("ckey", db.rs.getString("ckey"));
                 c.put("cvalue", db.rs.getString("cvalue"));
                 c.put("cdescription", db.rs.getString("cdescription"));
                 data.put("sys",c);
             }
         } catch (SQLException e) {
             System.out.println("SQL Exception: " + e.toString());
         }

         // Einzelwert
         HashMap item = (HashMap) data.get(0);
         System.out.println("Einzelwerttest: " +item.get(""));

         // ALle Werte ausgeben
         for (HashMap<String, HashMap> c : data) {
             for (String key : c.keySet()) {
                 System.out.println(key + ": " + c.get(key));
             }
         }

         // System.out.println(((HashMap)data.get(0)).get("Marke"));
         // System.out.println(((HashMap) data.get(0)).get("Marke"));
         // System.out.println(data);

     }
}