How to get values from a Map of Map in JAVA

Question

I'm trying to fetch all the values from Map inside a Map

DataType I'm using: Map<String, Map<String, Object>> userDetails = new HashMap<String, Map<String, Object>>();

Sample Data:

{
  "user1": {
    "admin": {
      "department_name": "Marketing",
      "first_name": "Peter"
    },
    "editor": {
      "department_name": "Sales",
      "first_name": "John"
    }
  },
  "user2": {
    "admin": {
      "department_name": "Advertisement",
      "first_name": "Emmanuel"
    },
    "editor": {
      "department_name": "HR",
      "first_name": "Anna"
    }
  }
}

I'm expecting to store all the values inside a List<Map<String, Object>>

[
  {
    "department_name": "Marketing",
    "first_name": "Peter"
  },
  {
    "department_name": "Sales",
    "first_name": "John"
  },
  {
    "department_name": "Advertisement",
    "first_name": "Emmanuel"
  },
  {
    "department_name": "HR",
    "first_name": "Anna"
  }
]