如何安全地从 Map 中检索 ArrayList<String, Object>

Question

How do I safely retrieve an ArrayList object from Map where the value stored for the key is an ArrayList. Below is my code. Is there any other way to do it instead of the cast to ArrayList?

public static void main(String[] args) {
    List<String> list = new ArrayList<String>();
    list.add("A"); list.add("B");

    Map<String, Object> map = new HashMap<String, Object>();
    map.put("list", list);
    System.out.println(map.get("list").getClass()); // class java.util.ArrayList
    List<String> l = (ArrayList<String>)map.get("list");
}

Answer 1

I was using the @JsonAnySetter from Jackson to store the Map<String, Object> . When I checked the class they are of class java. util.ArrayList java. util.ArrayList . (Same exact situation as explained in the question).

After trying few things I was able to get it. I know I am a bit late but hopefully, it will be helpful to someone in the future:

I had the Map<String, Object> the Object was storing either another Map , String , or ArrayList so I did the following things to get the values from my Map . You can use this as a reference and based on your required type you can do different things.

public void marshal(Map<String, Object> extensions) {
    for (Map.Entry<String, Object> property : extensions.entrySet()) {
       if (property.getValue() instanceof ArrayList) {
            for (Object dupItems : (ArrayList<String>) property.getValue()) {
                 if (dupItems instanceof Map) {
                    //do whatever you want to do Map type
                  } else if(dupItems instanceof String) {
                    //do whatever you want to do for String type
                  }
            }
        } 
    }
}