public static void nestedHashMap() {
HashMap<String, HashMap<String, Object>> map = new HashMap<>();
//--- Record 1 ---//
map.put("key1", new HashMap<String, Object>());
map.get("key1").put("key1a", "val1a");
//--- Record 2 ---//
map.put("key2", new HashMap<String, Object>());
map.get("key2").put("key2a", "val2a");
System.out.println("key1->key1a = " + map.get("key1").get("key1a"));
System.out.println("key2->key2a = " + map.get("key2").get("key2a"));
}